Eggless Custard Buttercream Frosting

March 1, 2010

This is a delicious frosting that whips up to a smooth and silky texture. I’ve made the chocolate and coffee versions and both are delicious. Here’s the chocolate version on my favorite chocolate cake.

Do not be turned off by the cornstarch! If you follow the directions and bring the mixture to a full boil and continue to boil it for 30 seconds, you won’t have any starchy flavor. Here’s what the milk/sugar/cornstarch mixture looks like after cooking. Very thick!

Eggless Custard Buttercream

from The Perfect Cake: 150 cakes for Every Taste and Occasion

[My notes in brackets]

1 cup plus 2 tablespoons (2 1/4 sticks, 260g) unsalted butter, softened but not melted
4 tablespoons cornstarch
1 1/4 cups milk [I used whole milk]
2/3 cup (4.5 ounces, 130g) granulated sugar

Flavoring: 2 teaspoons vanilla extract, or 1 tablespoon instant coffee powder dissolved in the milk, or 3 or 4 ounces semisweet chocolate, melted and cooled. [I used 4 ounces of 61% chocolate plus the vanilla; I’ve also made the coffee version]

1. In a bowl, beat the butter with a wooden spoon until soft and smooth; at this stage it will be readily incorporated into the custard.

2. In a small bowl, dissolve the cornstarch in 1/4 cup of the measured milk. Combine remaining milk with the sugar (and coffee if using it) in a 2-quart saucepan set over moderate heat. Bring the mixture to the boiling point, stirring on and off to dissolve all the sugar.

3. Stir the cornstarch mixture to be sure it has not settled. Whisk some of the hot milk into the cornstarch mixture to warm it, then pour the cornstarch mixture into the saucepan and whisk the ingredients over moderate heat for about 4 minutes while it comes to a full boil. Boil, stirring, for a full 30 seconds. The custard should be thick and smooth like a pudding [it’s really thick and sticky]. Remove pan from the heat and whisk hard until custard is smooth and glossy. Add the vanilla extract if using, or the melted and cooled chocolate if using [I used both].

4. Transfer custard to a clean metal bowl [I used my stand mixer bowl] and stir it over ice water for a couple of minutes, until completely cool to the touch throughout. If too warm, it will melt the butter. With an electric mixer [I used my stand mixer with the whisk attachment], beat the custard for a few seconds. With the mixer running, beat in the smooth butter, 1 tablespoon at a time, beating on high speed after each addition. After all the butter is incorporated, whip the mixture on high speed for a full 30 seconds. Use the buttercream at once or cover and refrigerate.

Makes 3 cups, enough to fill and frost an 8-inch 2- or 3-layer cake

Advance Preparation: The buttercream can be prepared up to a week in advance and refrigerated, or it can be frozen. Bring to room temperature and whip before spreading on a cake.


  1. This cake looks to DIE for delicious!


  2. That looks great! Mmm.

  3. Jill – this looks great – it’s similar to a flour-based buttercream I use (cooked on the stove with sugar and milk) then mixed with butter… I’ll have to give this a try, I love experimenting with new and different frostings!

  4. Sounds like the perfect buttercream frosting.

  5. This buttercream looks delicious – I’d love a slice of that enormous cake.

  6. I have never tried a buttercream like this. Very interesting. I look forward to trying it.

  7. Oh this looks good! I was looking for a good, kinda thick chocolate frosting. I will have to try this one!

  8. What an interesting technique – I need to try this! Looks delicious!

  9. Crazy! I’ve never tried a recipe like this. May have to give it a go!

  10. I love this frosting recipe! Thanks for sharing–it looks delicious!!

    Your cake is lovely!

  11. This looks like a super idea! I’ve been toying with making scratch pudding with cornstarch, but with a few mods for my particular intolerances this should work for frosting for me – how wonderful!

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