Preheat oven to 350 F (180 C) or 325 F (160 C) for glass dish.
In medium mixing bowl combine flour, sugar, baking powder and baking soda. Cut in butter and 1 tsp of the vanilla, until mixture resembles coarse crumbs. Press firmly on bottom of 13 x 9 pan. Bake 15 minutes or until lightly browned. Top evenly with marshmallows, bake 2 minutes longer or until marshmallows begin to puff. Remove from oven. Cool thoroughly. In heavy saucepan over medium heat combine eagle brand and chips. Cook and stir until slightly thickened, about 4 to 6 minutes. Remove from heat, stir in chow mein noodles, nuts and vanilla. Spread evenly over marshmallows. Chill thoroughly. Cut into bars. Store loosely covered, at room temperature. Makes 36 bars.