INGREDIENTS
3/4 cup
unsalted butter, softened to room temperature
1 cup
packed light or dark brown sugar
1
large egg + 1 egg yolk1
2 tsp
vanilla extract
2 cups
all-purpose flour (careful not to overmeasure)
2 tsp
cornstarch (aka cornflour)
1 tsp
baking soda
1/2 tsp
salt
1
and 1/2 cup (225g) semi-sweet chocolate chips
chocolate buttercream for topping (optional)