2 (11.5 ounce) packages milk chocolate chips, divided
2 cups butter
1 pound brown sugar
1 cup blanched slivered almonds, divided

Preheat oven to 200 degrees F (95 degrees C). Grease a 14 x 18 inch cookie sheet.
Sprinkle one package of chocolate chips on prepared pan. Place in warm oven until chips melt, about 5 minutes. Remove from oven, and spread melted chocolate over bottom of pan; set aside.
In a large heavy saucepan over medium-high heat, combine butter and brown sugar. Stirring constantly, heat to 300 to 310 degrees F (149 to 154 degrees C), or until a small amount of syrup dropped into cold water forms hard, brittle threads. Immediately remove from heat. Stir in 3/4 cup slivered almonds and pour onto pan with melted chocolate; spread mixture evenly.
Sprinkle remaining package of chocolate chips over the almond layer. The heat from the almond layer will melt the chocolate chips; spread melted chocolate evenly. Sprinkle remaining 1/4 cup almonds over chocolate.
Cut into squares, or allow to harden in a solid sheet and break it apart like brittle. Cool completely before removing from pan.