1 1/2 sticks (12 tablespoons) of unsalted butter

1 cup brown sugar

1/2 cup sugar

1 egg + 1 egg yolk, at room temperature

2 teaspoons vanilla extract

2 cups + 2 tablespoons all-purpose flour

1/2 teaspoons baking soda

1/4 teaspoon salt

1 cup toffee chips (such as Heath chocolate-covered toffee bits)

chocolate chunks, baking squares, or chocolate bars cut into pieces