Combine dry ingredients. Stir in molasses and sour milk and blend. Add raisins, stirring to mix well. Fill two 1 pint greased or oiled molds 2/3 full and cover with 3 thicknesses of waxed paper. Add 2 cups boiling water to cooker. Place molds on rack. Cover cooker and steam 15 minutes with pressure control lever open. Then cook under pressure 35 minutes. Allow cooker to cool at room temperature, then under cool water. Remove cover, run spatula between bread and mold to loosen, then invert on cake rack. Serve hot.