Heat oven to 350 degrees. In large bowl combine butter, flour and brown sugar. Blend until fine crumbs form. Press into 13x9x2 pan and sprinkle almonds over the top. Toffee topping: In small sauce pan combine 2/3 cup butter and 1/3 cup packed light brown sugar. Cook over medium heat, stirring constantly until mixture boils. Boil 30 seconds. Pour over almonds. Bake about 20 to 22 minutes until topping is bubbly and golden. Remove from oven and spread 1 package white chocolate chips over top to melt. Spread evenly as it melts. Cool completely on wire rack and then cut in squares.