Neapolitan Bars

For the pastry: Adjust rack in the middle of the oven and preheat oven to 350F. Set an ungreased 10 1/2 x 15 1/2 x 1-inch baking pan nearby.

Put flour, sugar and salt in a food processor fitted with the steel blade. Process just to blend. Scatter butter slices over the flour and process with on/off bursts until the mixture has the consistency of cornmeal.

Whisk egg yolks with vanilla in a small bowl. With the motor on, pour the egg mixture down the feed tube. Process just until ingredients form a ball.

Break dough into 8 equal pieces, and arrange pieces on the baking pan -- one piece close to each corner of the pan and the remaining 4 pieces just off the pan's center. Pat and spread the dough with your fingertips as best you can. Then, place a piece of plastic wrap on top of the dough and, with a short pizza-type rolling pin (or a can of soda), roll over the dough to cover the pan evenly. Remove the plastic wrap.

Bake for 15 minutes, or until set (the dough should not be shiny on top) and cream-colored. Remove to a wire rack to cool. Keep the oven on.

For the filling: Using a stand mixer, if available, fitted with the paddle attachment, beat the almond paste on lowest speed for about 2 minutes, until it is in fine crumbs. Add the sugar in a steady stream and beat at lowest speed until incorporated, about 1 minute. Add the butter, tablespoon by tablespoon. Stop the mixer, and scrape the mixture clinging to the sides down into the center of the bowl. Continue mixing while adding the eggs, one at a time, blending well after each addition. When batter is smooth, stir in vanilla, then a few drops green food coloring. If the filling appears lumpy, push it through a sieve.

To assemble: When the pastry has cooled, spread jam on top. Spoon the filling over the jam-covered pastry, spreading it slowly and carefully to avoid mixing the filling into the jam.

Return the pan to the oven and bake another 35 to 40 minutes, or until the pastry looks set on top and it's just firm, not solid, to the touch. (It might have a few light brown spots.) Remove from oven; set on a rack to cool completely before icing.

For the icing: In a 3-cup heavy saucepan over very low heat stir the butter, chocolate and milk just until the butter and chocolate melt, and a soft, smooth mixture forms. Remove from heat and stir in the vanilla and half the powdered sugar.

Transfer the mixture to a bowl. Stir in the remaining sugar until the mixture is smooth. If the icing looks dull or is too thick to spread, add additional warm milk, a teaspoon at a time. If too thin, add additional sifted powdered sugar, a tablespoon at a time.

Spread icing evenly over the filling. Set the pastry aside at room temperature for several hours before cutting into 1 1/2-inch squares.