Melt butter in a heavy saucepan; add brown sugar. Cook on low, stirring constantly, until mixture reaches 296 degrees on candy thermometer. Be sure it goes no higher than 296 degrees! Remove from heat; add 1 cup chopped almonds. Stir well and pour into a well-buttered cookie sheet. Spread over sheet and immediately frost with melted chocolate chips; sprinkle with remaining 1 cup of toasted almonds. Chill until set; break into pieces.