Whoopie Pies

Preheat oven to 375F. Sift together the flour, baking soda, baking powder, salt, cream of tartar, and cocoa. Set aside. In a large mixer bowl, cream the butter, lard, sugar, and vanilla together until well blended, about 3 minutes. Add the eggs, one at a time, blending after each addition. Add the flour mixture to the sugar-butter mixture, alternating with the milk and beginning and ending with the flour. Blend well, but don't over mix. The mixture will look like cake batter and if it appears curdled, don't worry. Cover cookie sheets with aluminum foil. Use 1/4 cup of batter for each cookie, drop them onto the cookie sheets--one in each corner, and one in the middle. Make them as round as possible. At this point, each cookie with be about 2 1/2 inches in diameter and they should be 3 1/2 to 4 inches apart. Bake for 6 minutes and, if necessary, reverse the cookie sheets from front to back so they bake evenly--I have to do this in my oven. Continue baking 10 minutes longer. The only sure way to tell if they are done is to touch them with your fingertip. If the top of the cookie springs back quickly, remove them from the oven; don't overbake. Slide the foil off the sheet and allow the cookies to stand for 2 minutes. Remove them from the foil with a metal spatula to wax paper-covered racks to cool. If any of the cookies are irregular, trim them carefully into rounds with a pair of scissors while they are still warm. (Reuse foil). Repeat with the remaining batter until you have 30 cookies. Meanwhile, prepare the filling. Place the flour in a medium saucepan, and add the milk gradually, whisking smooth. Cook over moderate heat, cooking and whisking until the mixture becomes thick and bubbles up in the center. Simmer over low heat for 2 minutes. Remove from heat and set aside to cool. Place the butter in a large mixer bowl and beat it until it is slightly softened. Add the salt, vanilla, and sugar gradually and beat for 2 minutes. Gradually, 1 large spoonful at a time, add the cooled milk mixture to the butter mixture. Then beat on high speed for 1 minute until the filling is smooth, light, and fluffy. If the filling seems too soft, refrigerate it until it firms up a bit. Arrange the cookies in pairs, flat sides up. Place a generous 1/4 cup of filling on 15 of the cookies, using all of the filling. Spread the filling to about 1/2 inch from the edge; it will be almost 1/2 inches thick. Top with another cookie, flat side down. Press the cookies together so the filling comes to the edges. Chill, then wrap each cookie individually in plastic wrap. Store in the refrigerator, but they taste better eaten at room temperature. They also freeze very well.