Chocolate Filled Walnut-Oatmeal Bars

INGREDIENTS

• 1 cup butter or 1 cup margarine, softened
• 2 cups packed light brown sugar
• 2 eggs
• 1 teaspoon vanilla extract
• 1/2 teaspoon powdered instant coffee
• 3 cups quick-cooking rolled oats
• 2 1/2 cups all-purpose flour
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 1/2 cups chopped walnuts, divided
• 1/2 cup butter or 1/2 cup margarine
• 2/3 cup hershey's cocoa powder
• 1/4 cup sugar
• 1 (14 ounce) can sweetened condensed milk (not evaporated milk)
• 1 1/2 teaspoons vanilla extract