Yields 360g of buttercream, or 1½ cup + 1 tablespoon, enough to generously frost 6-8 cupcakes.
Ingredients
130g (or ½ cup + 1 tablespoon + ½ teaspoon) unsalted butter, cubed and softened at room temperature*
220g (or 1¾ cup + ½ teaspoon) powdered sugar
45ml (or 3 tablespoons) heavy whipping cream
1½ teaspoons vanilla extract
fine table salt, to taste
a few drops op lemon juice, optional
Instructions
In a medium-sized bowl, using a mixer fitted with either a flat beater or a whisk attachment, beat the softened butter until fluffy and creamy, about 2 minutes.
Add the powdered sugar, cream and vanilla. Using a rubber spatula or a spoon, smush all the ingredients together until incorporated, then mix with a mixer until smooth, fluffy and creamy, and the buttercream has lightened in color, about 3-5 minutes.
Taste the buttercream to see if it needs any salt. If the buttercream is too sweet for your taste, sprinkle a pinch of salt over the surface of the buttercream. Mix briefly to incorporate, then taste again. Add more salt, a pinch at a time, if the buttercream is still too sweet for your taste.
Once you're happy with the sweetness, add a few drops of lemon juice (optional) to brighten the flavor. Mix well to incorporate.
Finally, use a rubber spatula to smush the buttercream against the sides of the bowl to get rid of any large air bubbles. This makes piping the buttercream a lot easier.
Use immediately or store, covered in the fridge, for up to seven days. Before you want to use it, allow buttercream to come to room temperature and mix briefly until smooth and creamy again.
Buttercream can also be frozen in a zip-lock bag for up to two months. Allow to thaw in the fridge overnight, then allow to come to room temperature and mix until smooth and fluffy before use.
Frosted cakes or cupcakes stay fresh, covered at room temperature, for up to three days.
Notes
* I usually take the butter out of the fridge 30 minutes before I want to start mixing.