Swiss meringue buttercream

Set up a double boiler: a medium pot with about two inches of water heated over medium-high, then reduced to a simmer; the water must never touch the bowl.

Separate the eggs one at a time so no yolk gets into the whites.

Add the granulated sugar to the whites and whisk briefly to mix.

Set over the simmering water and stir occasionally, then more often as it warms, scraping the hot edge of the bowl, until it reaches 160 degrees and no sugar granules can be felt.

Optionally wipe the mixer bowl with vinegar to remove any fat, then add the hot egg mixture.

Whip on high until a stiff, glossy meringue forms and it cools to around room temperature, about 75 degrees; usually 10 to 15 minutes. Add a generous pinch of salt while it mixes; frozen peas pressed against the bowl speed cooling.

Cut the room-temperature butter into tablespoon pieces.

Switch to the paddle and, on low speed, add the butter a tablespoon at a time; keep adding through the soupy stage, scraping the bowl down once.

After the last butter, mix a minute more, increasing to medium, until it turns cloudy and smooth with no lumps. If still gloopy, chill 5 minutes and mix again, repeating as needed.

If it sits or is stored and turns foamy, whisk 30 seconds to bring it back to silky.

Flavor as desired, e.g. vanilla, melted chocolate, caramel or brown butter.

Variation: for a saturated color, microwave a couple of tablespoons of frosting with plenty of gel color for 30 seconds to melt, then mix it into the batch.

Variation: for chocolate buttercream, mix in melted chocolate to taste; it sets up firmer.

Fill a piping bag and pipe.