Grandma's Ermine Buttercream (Old-Fashioned Flour Frosting)

This is my grandmother's ermine buttercream — the old-fashioned flour frosting that has been quietly upstaging every cake in my family for as long as anyone can remember. If you've only ever had American buttercream, the kind built on an avalanche of powdered sugar, this is going to feel like a revelation: silky, buttery, genuinely light, and just sweet enough.

Family lore — and I want to be clear that it is lore, not documented history — holds that Grandma got this recipe from a chef at the Waldorf-Astoria. Did a hotel chef really hand my grandmother his frosting recipe? We'll never know. But I choose to believe it, the same way I choose to believe every story she told with that particular glint in her eye.

This frosting also happens to sit at the center of the greatest scandal in this blog's history, which you can read all about below the recipe. But first: the frosting itself, because that's what you came for.

What Is Ermine Frosting?

Ermine frosting — also called flour frosting, boiled-milk frosting, or cooked-flour frosting — is the buttercream your great-grandmother probably made, and it's the frosting red velvet cake originally wore before cream cheese muscled in. The method sounds odd the first time you hear it and makes perfect sense the first time you taste it:

1. Cook flour and milk together into a thick, pudding-like paste.
2. Cool it completely.
3. Whip it into butter that's been creamed with granulated sugar until the whole thing turns into a cloud.

That cooked base is what makes ermine special. It carries the dairy flavor and the structure, so you don't need pounds of powdered sugar to make the frosting hold its shape.

Why It Beats American Buttercream

I'm going to be opinionated here, because this is my blog and that's the arrangement: ermine is simply better than American buttercream for most cakes.

• It's far less sweet. One cup of granulated sugar for the whole batch, versus the four-plus cups of powdered sugar in a typical American buttercream. You taste butter and vanilla instead of pure sugar.
• It's silky, not gritty. The sugar dissolves as you cream and whip, and the cooked base gives it a texture closer to whipped cream than to frosting-tub spackle.
• It spreads and pipes beautifully. Rosettes, lattices, borders — it holds all of them at room temperature.

Fair warning on the trade-offs, because honesty is a theme around here: ermine is softer than American buttercream in a hot kitchen, and it doesn't form that dry crust some decorators rely on. On a July porch, plan accordingly.

The One Rule That Matters: Temperature

If ermine frosting has a reputation for being fussy, it's because of one single thing, and it isn't the cooking — it's the temperature at the moment the two mixtures meet.

The butter and the cooked flour base should be as close to the same cool room temperature as possible when you combine them. That's the whole secret.

• If the flour base is still warm, it melts the butter and you get soup.
• If the base (or the butter) is too cold, the butter seizes into little curds and the frosting looks broken and separated.

Neither is fatal. Keep beating — it very often comes back together on its own. If it stays soupy, the mix is too warm: park the bowl somewhere cool for 10–15 minutes and beat again. If it stays curdled, it's too cold: let it warm up on the counter for a few minutes and beat again. What you should not do is blast it with heat or stick it in the freezer and hope. Patience and the mixer will fix what temperature broke.

This is also why the recipe says to cool the flour base at room temperature rather than in the refrigerator. The fridge cools the outside of the mixture faster than the inside, and it's easy to end up with a base that's cold in some spots, warm in others, and ready to break your emulsion in both directions at once.

Storage (or: Why I No Longer Tell You to Chill It)

A housekeeping note for returning readers: an earlier version of this recipe listed 2 cups of milk and ½ cup plus 2 tablespoons of flour — double the cooked base that one cup of butter and one cup of sugar can actually absorb — and told you to chill the finished frosting before using it. Both of those were wrong, and both are fixed below. If you made the old version and ended up with something loose and strange, that was my error, not yours. Consider this my own scandalous correction.

This frosting is at its absolute best the day it's made, used at room temperature. It does not need to be chilled before spreading — in fact, chilling works against it, because cold butter is exactly what makes it stiffen and break.

That said, life happens. If you need to make it ahead, refrigerate it in an airtight container for up to about five days. Just know what you're signing up for: the fridge firms the butter, so the frosting will come out stiff, and the emulsion may look temporarily broken. To revive it, let it come fully back to room temperature — an hour or two on the counter, and no, you cannot microwave your way out of this — then re-whip it until it's smooth and fluffy again. It comes back beautifully as long as you don't rush it.