Root Beer with margarine

1 1/4 cups all-purpose flour 3/4 cup sugar 1/3 cup butter or 1/3 cup margarine , softened 3/4 cup root beer 3/4 teaspoon baking powder 1/2 teaspoon salt 1/4[...]

1 cup dark brown sugar , packed 4 ounces margarine 4 tablespoons unsalted butter , at room temperature (1/2 stick) 1 large egg 1 teaspoon vanilla extract 1/2[...]