Preheat oven to 350°. Beat butter and sugars at medium speed with a heavy-duty electric stand mixer until creamy. Add eggs and 1 1/2 tsp. vanilla, beating until blended.
Combine flour, baking soda, and salt in a small bowl; gradually add to butter mixture, beating just until blended. Beat in chopped toffee candy bars and slivered almonds just until combined. Drop by tablespoonfuls onto parchment paper-lined baking sheets.
Bake at 350° for 10 to 14 minutes or until desired degree of doneness. Remove to wire racks, and cool completely (about 15 minutes).