Cream margarine and sugar; add eggs one at a time, beating well after each addition.
Sift flour over nuts; add to creamed mixture with vanilla.
Pour batter into 9 x 9 x 2-inch greased floured pan.
Drop choco- late by spoonfuls over batter.
Bake at 300 degrees for 15 minutes; reduce heat to 325 degrees.
Bake for 15 minutes longer.
Remove from oven; cool on rack.
Ice with fudge frosting, if desired.