Preheat oven to 350 degrees Fahrenheit. Grease and line a seven- by 11-inch tin pan with wax paper.

Dissolve coffee in boiling water.

Cream margarine, peanut butter, sugar, and coffee until light.

In a separate bowl, sift together flour and cornstarch.

Mix flour mixture into creamed mixture to make smooth dough. Press dough into the bottom of the pan and prick all over with a fork.

Bake for 20 minutes. Meanwhile prepare topping.

Heat margarine, brown sugar, and syrup in a pan until melted.

Bring mixture to a boil. Simmer for five minutes, and then stir in nuts.

Spread topping evenly over base.

Leave in pan until cooled. Cut into squares or bars. Remove from pan and serve.