Toffee Squares

1 cup margarine
1 cup brown sugar
1 egg yolk
1 tsp vanilla
2 cups flour
1/4 tsp salt
4 7/8-oz chocolate bars (I use Nestle Crunch bars)
1/2 cups chopped pecans or hazelnuts

Preheat oven to 350 °F.

Mix margarine, sugar, egg yolk, and vanilla; stir in flour and salt until well blended. Spread in 10x13 greased cookie sheet. Bake 20-25 minutes until brown. Remove from oven. Immediately place separated squares of chocolate on top. Let stand until soft; spread evenly over entire surface. Sprinkle with pecans. Cut into squares while warm.