These easy-to-make squares have a buttery base topped with a thin layer of chocolate and nuts.
Cream butter and brown sugar. Add egg yolk. Add flour and vanilla, and stir until well blended. Spread dough into a greased 15x10x1-inch jelly-roll pan and bake at 350 degrees F for 15 to 20 minutes, or until golden brown. Remove from oven and immediately sprinkle chocolate chips on top of crust. Allow chocolate to soften, and spread evenly. Sprinkle with chopped nuts and press nuts lightly into chocolate, using the bottom of a glass. Cool, then cut into squares.