Melt over low heat the butter, remove from heat and stir in brown sugar and cool. Stir in eggs. Sift together flour, baking powder, salt. Add vanilla and nuts. Mix all well. Spread in a well greased(not floured) pan and bake until ingredients- when touched lightly with finger only a slight imprint remains. Do not overbake. Cut into bars while still warm. Bake about 25 minutes @350. makes about 3 dozen. Freezes well.