Swiss meringue buttercream

Put an inch or two of water in a medium pot over medium heat and bring to a simmer.

Separate five egg whites into a medium bowl with no trace of yolk.

Add the granulated sugar and a pinch of salt and whisk to combine; it should feel sandy.

Set the bowl over the simmering water without touching it, stirring occasionally, then constantly as it warms, until it reaches 160F, the sugar has dissolved and it feels hot to the touch; keep the thermometer probe off the bowl.

Take it off the heat; make sure the mixer bowl is completely free of fat, wiping with lemon juice or white vinegar if in doubt.

Whip the hot meringue with the whisk attachment, starting on low and moving to medium-high, until it forms thick, sharp marshmallowy spires.

Keep mixing on medium about 10 minutes until it cools to room temperature (mid-70s to low 80s); frozen peas packed round the bowl speed this up.

Switch to the paddle and on low add the butter one tablespoon at a time, mixing a few seconds between each, scraping the bowl; it turns soupy until the last of the butter goes in.

If it is still soupy at the end, chill 5 minutes and mix again; repeat if needed.

Store sealed in the fridge up to a week or the freezer up to a month; rewhip on high about 30 seconds before use.

Add the vanilla, scrape the bowl and whip briefly on high.

If it is too thick from a cold bowl, microwave about 10 seconds at half power (or warm with a hairdryer) and whip again.

Variation: for chocolate, mix in melted and cooled chocolate until no streaks remain.

Variation: to color, melt about a tablespoon of buttercream with a drop of gel food coloring in the microwave about 20 to 30 seconds and mix it back into the batch.

Whip a few seconds, fill a piping bag and pipe onto cupcakes at once.