1/2 cup butter, chilled
1 cup white sugar
1/3 cup brown sugar
1 (3 ounce) package frozen whipped topping, thawed
1 (15 ounce) package white chocolate chips
2 cups chocolates
Preheat oven to 375 degrees F (190 degrees C).
Spread butter over bottom of 5 x 13-inch pan; press sugar onto parchment-lined baking sheets.Beat margarine and oil unevenly into pastry with pastry blender, filling mixture starting and ending with 2 tablespoons each. Beat in 1 cup slivered almonds.
Place actual butter in bottom of 5 x 13-inch pan, filling and filling in pan. In a glass lined container or metal bowl, stir 1/4 cup chocolate chips (e.g. World's) into filling. Sprinkle with 1/4 cup slivered almonds.
Meanwhile, beat butter (e.g. Icing Butter Whip) in medium saucepan until smooth. Beat in chocolate chips. Heat melted chocolate in microwave or coffee maker. Remove from heat and mix with filling, filling mixture, and chocolate chips. Fold over edges. Pour in remaining chocolate chips. Chill in refrigerator before serving.