Heath Bar Coffee Cake

2 cups all purpose flour
1 cup (packed) dark brown sugar
1/2 cup sugar
1 stick unsalted butter, room temperature
1/2 teaspoon salt
6 1.4-ounce Heath Bars, chopped
1 cup chopped pecans or walnuts
1 teaspoon baking soda
1 cup buttermilk
1 large egg
1 tablespoon vanilla extract
1 tablespoon Kahlua liqueur, optional

Preheat oven to 350 F. Butter 13x9x2-inch glass baking dish. Using electric mixer, beat first 5 ingredients in large bowl on low speed until mixture resembles coarse meal. Transfer 3/4 cup butter-sugar mixture to medium bowl; mix in toffee and pecans.

Set aside. Stir baking soda into remaining butter-sugar mixture in large bowl. Add buttermilk, egg and vanilla, beating until just combined. Transfer batter to prepared dish.

Sprinkle toffee topping evenly over batter. Bake until topping is golden brown and toothpick inserted into center of cake comes out clean, about 35 minutes.

Cool completely in baking dish. Cut into 16 squares.

Store in airtight container at room temperature.

Yield: Makes 16 squares.