Make sure the cream and compote are very cold. It’s also helpful to put the bowl and beaters in the fridge if you have time. In a chilled bowl, beat the heavy cream until it begins to thicken.
1 cup (237 ml) heavy cream
Add 1 tablespoon powdered sugar and the vanilla, and continue beating until you reach stiff peaks (the cream should stand straight up when you lift the beaters). Taste and add the remaining powdered sugar, if desired.
1-2 tablespoons powdered sugar, 1/2 teaspoon vanilla extract
Add 1 cup of the chilled compote. Using a large spatula, fold the compote very briefly, only 2 or 3 turns. You want to see distinct white and pink streaks. Immediately spoon the mixture into your glasses.
1 cup (255 grams) above rhubarb compote
Top each glass with a tablespoon (or more) of the remaining compote. Chill for 30 minutes to let the flavors marry and the structure firm up.
The assembled fools are best made shortly before serving, but they can be chilled for a few hours. Store any leftovers in the refrigerator for up to 2 days. The texture will soften slightly as it sits.