Ermine Frosting (Cooked Flour Frosting)

Before you start

Ermine frosting, also called boiled milk or flour frosting, begins as a stovetop pudding of milk, sugar and a little flour. Once the paste has cooled completely, it is beaten into whipped butter, producing a light, fluffy frosting that some describe as tasting like whipped cream with more body. It is widely associated with early red velvet cakes, though origin stories differ, and it is far less sweet than powdered-sugar frostings.

There are two keys. Cook the paste until it is as thick as stiff pudding, so the flour loses its raw taste and the granulated sugar fully dissolves. Then cool it all the way to room temperature, not just warm, before beating it into butter that has been whipped until pale. If the paste is warm, the butter melts; if either is cold, the frosting looks curdled. When both are at about 21°C (70°F), it comes together in a few minutes into something glossy and smooth.

Ingredients

• Paste40 g (5 tbsp) all-purpose flour
• 200 g (1 cup) granulated sugar
• ⅛ tsp fine salt
• 240 ml (1 cup) whole milk
• 2 tsp vanilla extract
• Butter225 g (1 cup) unsalted butter — softened to about 20°C (68°F)

Method

1. Whisk the flour, sugar and salt together in the cold saucepan. Pour in the milk a little at a time, whisking, so the flour dissolves without lumps.
2. Cook over medium heat, whisking constantly, until the mixture thickens and starts to bubble, 5 to 7 minutes. Keep cooking and whisking for 1 to 2 more minutes, until it is very thick, like a stiff pudding that holds a trail.
3. Take it off the heat and stir in the vanilla. Rub a dab between your fingers: it should feel smooth, with no sugar grains. Scrape it into the shallow dish.
4. Press plastic wrap onto the surface and let the paste cool completely at room temperature, about 1½ hours. It should feel neither warm nor cold. Do not rush it in the refrigerator unless you let it warm back up.
5. Beat the softened butter on medium-high for 4 to 5 minutes, until pale, fluffy and nearly white.
6. With the mixer on medium, add the cooled paste a heaping spoonful at a time, letting each one blend in. Then beat on medium-high for 2 to 3 minutes, until smooth, light and holding soft peaks.
7. Use it right away at room temperature. It spreads beautifully and pipes simple swirls and borders, though it is softer than a crusting buttercream.

Tips for success

• Whisk constantly while cooking; flour paste sticks and scorches on the bottom quickly once it thickens.
• If you see a few lumps in the hot paste, push it through a fine sieve before cooling.
• Ermine frosting holds up best in a cool room. In warm weather, chill the frosted cake and bring slices out shortly before serving.

Substitutions

Whole milk

Use half milk and half heavy cream for a richer, slightly firmer frosting. Low-fat milk works but tastes lean.

All-purpose flour

Use 30 g (¼ cup) cornstarch for a glossier, more translucent paste. It sets a little firmer, so cook it just until thick.

Granulated sugar

Light brown sugar gives a caramel-tinted frosting that suits spice and banana cakes.

Variations

Chocolate ermine frosting

Whisk 25 g (¼ cup) cocoa powder into the flour and sugar before adding the milk.

Brown sugar and bourbon

Use brown sugar in the paste and beat in 1 tbsp bourbon at the end.

Troubleshooting

Frosting looks curdled or separated

The paste and butter were at different temperatures. If the paste was cold, warm the bowl gently while beating; if it was warm and greasy, chill 10 minutes and beat again.

Frosting is soupy

The paste was still warm or was not cooked thick enough. Chill the bowl 15 minutes and beat again; next time cook the paste until very thick.

Gritty or floury taste

The paste was undercooked. Cook it a minute or two past the first bubbles, until thick and smooth.

Storage

Refrigerate the frosting or a frosted cake, covered, for up to 4 days. Before re-beating leftover frosting, let it come back to room temperature. Because it is made with cooked milk, do not leave it out longer than 2 hours.

Safety notes

Ermine frosting is made with milk, so treat it as perishable: refrigerate it and do not leave it at room temperature for more than 2 hours. Contains milk and wheat.