Preheat oven to 350 degrees F. Butter and flour a 1/2 sheetpan or jelly roll pan. Sift the dry ingredients together and set aside. In an electric mixer cream the butter, molasses and sugar until light and fluffy. Beat in the egg and add the reserved dry ingredients and mix until just incorporated. Fold in oats, raisins and nuts. Spread dough in an even layer on prepared sheetpan and bake for 20 to 30 minutes or until lightly browned. Let cool on a rack for 10 minutes then carefully cut into bars approximately 3 inches square. Remove bars from pan and allow to cool completely.