In a medium bowl, cream together the sugar and butter. Stir in the molasses, vanilla and egg yolk. Add flour, mix until combined. Press dough into the bottom of a 20x30cm baking dish. Bake for 20 to 25 minutes, until golden brown.
In a 2 litre saucepan, combine raisins, peanut butter and chocolate chips. Melt over medium-low heat, stirring constantly. Spread evenly over the baked crust and refrigerate until set, about 1 to 2 hours. Cut into bars and serve.