1/2 cup butter
2 1/4 cups chocolate chips
1/3 cup white sugar
1 cup unsalted butter, melted
1/2 cup semisweet chocolate chips
Preheat oven to 350 degrees F (175 degrees C). Press chocolate chips and sugar into a medium bowl; set aside.
In a medium bowl, cream together 1/2 cup of butter and chocolate chips. Beat in 2 1/2 cups of sugar, one cup at a time. Continue to beat until the mixture is smooth but not clumpy, about 5 minutes. Stir in the melted butter and chocolate chips. Press mixture evenly into an 8x8 inch casserole dish.
Bake in the preheated oven for 25 to 30 minutes, or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes before cutting into squares.