1 cup unsalted butter (2 sticks - softened!)
1/2 cup fresh strawberries, cut into small chunks
1/4 cup powdered sugar
You'll also need a hand mixer and a sieve.
Try to get the juiciest, most strawberry-smelling strawberries you can find. Greenhouse/unripe strawberries just do not do this dish justice.
I do not recommend using normal sugar for this recipe - it can turn the butter into a grainy mess.