> 6 tbsp unsalted butter, softened, plus more for greasing
> 3/4 cup packed light brown sugar
> 1/2 tsp salt
> 1 large egg
> 1 tsp vanilla extract
> 1 cup all-purpose flour
> 3 tbsp unsweetened cocoa powder
> 1/2 tsp baking soda
> 1 1/2 cups milk chocolate chips
> 1/2 cup white chocolate chips
Preheat oven to 350°F. Lightly grease bottom of a 10-inch oven-safe skillet. In a large bowl, mix the butter, sugar, and salt until creamy. Beat in the egg and vanilla. Mix in the flour, cocoa powder, and baking soda. Fold in the milk chocolate chips.
Spread dough in prepared pan in even layer all the way to edges. Bake 20–25 min., until toothpick inserted in center comes out clean. Cool completely in skillet on wire rack. Invert onto cutting board and cut into 16 wedges. Arrange wire rack over a large piece of waxed or parchment paper. Arrange cookies on wire rack.
Place the white chocolate chips in a microwave-safe bowl. Microwave in 15-sec. intervals until melted, stirring in between. Let cool slightly. Drizzle white chocolate over cookies. Let stand until set. To store, keep in a sealed container at room temperature for up to 5 days.
Tint the white chocolate with green food coloring before drizzling. Then decorate with sprinkles on top of chocolate before letting chocolate set.