How to Fix Runny Custard in 3 Easy Steps


Having custard come out runny can be rather frustrating, to say the least. However, don’t feel bad if this happens, as it is a fairly common occurrence. Even though it seems to be such a simple recipe to make, it takes both good technique and ingredients to get it right.

Runny custard can often be fixed by adding a thickener. Create a slurry by adding one tablespoon of cornstarch, tapioca, or arrowroot, or two tablespoons of flour, to 4 tablespoons of water per cup of custard. Then whisk until well blended. While the custard is being heated, mix in the slurry.

By the way, the value of a good whisk, like the simple but effective one I use (From Amazon) cannot be overstated. In fact, it might be my favorite tool in the kitchen and is great for tasks like this!

Now that you know the basics of how to rescue runny custard, the rest of the article will go into more detail and answer a few common questions.

Why Is My Custard Watery?

If your custard looks more like a soup than the image on the box, you’ve likely added too much milk. If you’re cooking it from scratch, it might be because you didn’t cook the eggs properly.

Pastry making is science and, not only do you have to get the ratio of ingredients right, but there’s no skipping steps either.

What Consistency Should Custard Be?

Depending on the intended purpose, custard can be either runny (i.e., ice cream) or set custard (i.e., pudding or clafoutis). The biggest difference between the two is that the former is set only by cooking egg yolks, while the recipes for the latter often include some type of starch or another thickener.

Pouring custard is usually of the same or slightly thicker consistency as egg not (which is not too strange since they are more or less the same thing). At its thickest, it should pour like double cream.

Set custard can be as firm as jello or slightly softer and fluffier. Firm custard is usually preferable in the building of other desserts like fresh fruit tarts or entremets.

How Do I Make My Custard Thicker?

When custard is too runny, does this mean you should toss it out? Not necessarily. We can try to rescue it, and here’s how.

Starch to the rescue.

A pot of runny custard sitting on the stove right now? You followed the recipe or instruction to the letter, and it still doesn’t look right? Time to add some starch.

Step 1 – Choose your thickener wisely

Most starches are going to make the custard a bit matte and/or cloudy. It’s not a bad thing if you don’t mind it, but if the high gloss is what you’re looking for, pick tapioca or arrowroot.

If the plain cornstarch is all you have at hand, you can add a knob or two of butter to restore some of the glossiness. Flour will work as well, but just use twice as much of it.

Step 2 – Make a slurry

You can’t just dup the starch powder into the pot since it will clump in one place and stay there.

To make the slurry, mix 4 tablespoons of water or milk with 1 tablespoon of starch (or 2 tablespoons of flour) until smooth. This amount will work on 1 cup of finished custard, so adjust accordingly.

Step 3 – Rescue the custard

Keep the custard on the heat when you add the slurry. Mix thoroughly with a whisk and then switch to the spatula to continue cooking.

Once the custard looks like it’s of the right consistency, do the back-of-the-spoon test by drawing the line with your finger. If the line holds, your custard is perfectly cooked.

Temper, temper

Egg tempering is probably one of the messiest and sometimes scariest things that you can do in your kitchen, but you should not skip it. If you do, the eggs will curdle instead of mixing through the milk and setting the custard.

Here are a few tips that will make this step less scary:

  • Tip 1- Use room-temperature eggs and add granulated sugar. While you’re whisking in and dissolving the sugar, you’ll bring the egg temp up by a few degrees. This will also lighten the eggs, so they mix through the milk quicker.
  • Tip 2- Roll a kitchen towel into a donut and set it under the bowl containing the egg and sugar mixture. This will keep it from moving once you start pouring in the hot milk. It will also catch drips and protect your counter from milk stains.
  • Tip 3- Pour the milk into a heat-proof vessel with a spout like a pyrex measuring jug or a french press. This will lower the temperature of the milk by few degrees, and it will also make it easier to pour it into the egg bowl in a steady stream.

Yes, it’s an extra thing then needs washing up, but it’s a lifesaver until you become a pro at egg tempering.

All-in-one shortcut

There is a shortcut to getting perfectly set yolks every time, but it requires special equipment. Meaning, you’ll either need a sous vide machine or another appliance that can maintain a consistent cooking temperature.

Once you acquire all of the heavy machinery, just blend the ingredients and cook at 176°F until it reaches desired consistency. The custard will be slightly runny right after, but the residual heat will finish it cooking to perfection.

Bad recipe

If the previous two solutions didn’t help, you are dealing with a bad recipe. Or you’re not using appropriate measurements.

In baking (and yes, custard under this umbrella), exact measurements are vitally important. So, switch from using cups and tablespoons to ounces and grams.

But a bad ratio of ingredients can also lead to disaster. Sugar is, technically, a liquid, and too much of it will make the custard runny. In a recipe without starch, one egg yolk will set up to 3.5 ounces of milk or cream, and too much will also make the custard runny. Not to mention what would happen if you randomly add margarine instead of butter for glossiness…

If the custard never comes out right, no matter what you do, it’s time to either break out the kitchen scales or pick a new recipe altogether.

Why Does Custard Go Watery In the Fridge?

There could be a couple of reasons, but one possible culprit is the moisture in the fridge. If you’ve made the custard from the box (or a packet), it can continue to absorb moisture from the environment. Always make sure to wrap the bowl tightly before you place it in the fridge.

Or you could be dealing with expired ingredients. Whether it’s old eggs or a boxed custard that is past its prime, all thickening and emulsifying components need to be fresh to do their job correctly.

And on a similar note, you may have overcooked or undercooked it. You know how when you make scrambled eggs, they start releasing liquid? That’s due to the degradation of lecithin, a very important emulsifier that keeps water and oil from splitting.

Similarly, starches also have a temperature sweet point – going too low, and you will fail to “activate” them, and going too high and for too long will break them down into sugar (the same way a potato becomes sugar and then becomes vodka).

Final Bite

In summary, runny custard can be fixed in three easy steps:

  1. Make a slurry with water and a thickener.
  2. Whisk until blended well.
  3. Pour the mixture back into the pot and heat until thickened, constantly stirring over medium-low heat for about 5 minutes or until thickened. Remove from heat immediately after thickening has occurred.

ProTip: Use vanilla beans or vanilla extract in your custard recipe to give it a deliciously creamy flavor. Our family enjoys vanilla custards, and thanks to one member’s gluten-free diet, we were forced to try using coconut flour as a thickener. The result was an intensely creamy texture that rivaled the taste of traditional custard. Since then, our family has grown fond of this particular recipe, and we’ve even modified it to make creme brulee and chocolate cream pie!

This is an excellent option for those on dairy-free diets or who incorporate alternative sweeteners into their diet because it is entirely natural and contains no added sugar.

I hope this article has been helpful.

A Message from Jelly Grandma: Hey y’all! I started a YouTube channel called “Preserving Sweetness” that focuses on sharing tips that I’ve learned over the past 55+ years. Please come subscribe and check out the ridiculously unpolished videos. It would be a HUGE help to me. Thanks!

For more, don’t miss Why Do My Pancakes Fall Apart? | How to Fix It.

Anne James

Hi, I'm Anne but my grandchildren call me Jelly Grandma. I have over 50 years of experience as a Southern cook and am a retired librarian. I love sharing what I have learned. You can find me on YouTube as well! Just click the link at the bottom of your page. I hope your visit here has been a sweet one.

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