Mousseline Buttercream Frosting
Using only egg whites gives this frosting a lovely white hue, but it’s also easy to color with food colorings. It’s soft enough to pipe borders and stiff enough to pipe flowers and other embellishments. Customize it with flavoring extracts or flavored liqueurs and spirits such as bourbon, vodka or rum.*
- 1 cup sugar
- 1/4 cup (2 fluid ounces) water
- 5 large (5 fluid ounces) egg whites, room temperature
- 1/2 teaspoon cream of tartar
- 4 sticks (2 cups) unsalted butter, room temperature
- Vanilla or other flavored extract, to taste
- 3 fluid ounces bourbon* (or any spirits or flavored liqueur)
- Food coloring
- BRING sugar and water to a boil in heavy-bottomed saucepan and heat until it reaches soft-ball stage (265℉). WHISK egg whites and cream of tartar together in the bowl of an electric mixer fitted with a whisk attachment. Whisk until firm peaks form.
- REMOVE hot sugar from stove and pour into a heat-resistant measuring cup. With the mixer on, slowly pour hot sugar into egg whites mixture, avoiding hitting the whisk. Keep whisking on high until egg whites are completely cooled.
- ADD butter a little at a time, waiting for each addition to be incorporated before adding more, until all butter is incorporated. Add flavoring or food coloring if using (optional).
1.*Frostings with bourbon or other alcohol-based spirits added are not suitable for children, as the alcohol in them remains full strength and does not evaporate or “cook out.”
2. Butter should be room temperature but not too soft; it should hold a finger imprint when touched. Take butter out of fridge 20 minutes before starting recipe, cut it in cubes and let it sit out until ready to use.
3. Make sure meringue is completely cool after adding hot sugar to it, before adding butter. If it is still warm, it will melt the butter.
4. If frosting looks like it has separated (usually toward the end) don’t worry, this is normal. Just keep the mixer on high and it will come together and smooth out.