Buttery shortbread, a layer of toffee, and chocolate topping make these cookie bars a favorite sweet among families in Ireland. Invite your kids to help make a batch for a special St. Patrick's Day snack.
Shortbread: Preheat the oven to 350°. In a bowl, cream together the softened butter and sugar. Stir in the flour until well mixed. Press the batter into a 9-inch square pan (a good job for kids). Bake for 25 to 30 minutes, until the edges are golden brown. Let cool.
Toffee: Melt the 1/2 cup of butter in a heavy saucepan over medium heat. Add the brown sugar, condensed milk, and corn syrup, and bring the mixture to a boil. Cook for 5 minutes, stirring continually. Remove from the heat and stir in the vanilla extract. Pour over the cooled shortbread.
Topping: Melt the chocolate chips in a double boiler or a microwave oven. Stir until smooth. Pour over the cooled toffee. Cut into 16 squares.