Preheat oven to 350°F. Line a standard muffin tin with paper liners.
In a medium bowl, beat butter and sugar together until light and fluffy. Add egg and vanilla extract and beat until well combined. Sift in flour, baking powder, and salt and beat until just combined.
Fill each cupcake liner with 1 tablespoon of batter. Bake for 18 minutes, or until cupcakes are lightly golden brown and a toothpick comes out clean when inserted into the center. Let cool completely.
Once cupcakes are cool, use a spoon or an ice cream scoop to hollow out the center of each cupcake until it's about 1/2 inch thick.
Fill each cupcake with a scoop of vanilla ice cream and serve immediately!