These shortbread-type cookies will melt in your mouth. Maria typically makes them for the winter holidays and for the end of the Easter meal. The most important ingredient, in her estimation, is the unsalted margarine.
Heat oven to 350°. In a standing mixer, cream together 1 stick each of margarine and butter. At slow speed, add oil; then speed up and mix until smooth. Lower speed and add confectioners’ sugar; then speed up to mix. Add eggs and blend until smooth. Add vanilla and mix well, about 5 minutes. Add walnuts and baking powder and mix another minute. Add flour, one cup at a time, mixing well between additions. Turn mixer off and finish mixing by hand until dough is a solid lump (not too sticky, but not dry and crumbly). Let it rest 15 minutes. Roll dough into 1-inch balls and press onto ungreased baking sheets until they’re about ½-inch thick. Bake 20 minutes, until slightly golden. Cool about 5 minutes on baking sheets. Then gently, but thoroughly, dredge them in confectioners’ sugar. Serve warm for the most delicious flavor.