Add milk, 1 tablespoon at a time, and pulse until mixture forms a ball. (Depending on humidity, dough requires 3 to 6 tablespoons of milk.) Remove dough, shape into two 5-inch discs, wrap in plastic wrap and refrigerate at least one hour.
If you're making the tart, roll out one disc of dough to 1/8-inch thickness; it should be 1 to 1 1/2 inches larger than a 9-inch tart pan (with removable bottom). Carefully fit dough into pan so that it flops over the edge by 1/2 inch. Using a rolling pin, roll over top of crust to create an even edge. Chill dough thoroughly.
Preheat oven to 400°F. With tines of a fork, press into bottom of dough. Cover with foil and place pie weights, uncooked beans or rice inside shell. Cook 15 to 20 minutes. Carefully remove foil and weights, then continue baking 5 to 10 minutes, until golden brown. Cool on rack.
If you're making cookies, roll out dough to 1/8-inch thickness. Using a sharp knife or small cookie cutters, make desired shapes. Place cookies on an ungreased baking sheet; freeze 10 minutes.
In a small bowl, make a glaze by combining egg yolk and cream. With a pastry brush, glaze each cookie; sprinkle generously with granulated sugar. Bake 8 to 12 minutes, or until light golden brown. Remove from oven; cool.
Using a zester or the smallest holes on a grater, zest lime and lemons; place in a glass measuring cup. Juice limes and lemons (about 1/2 cup) and add to zest.
In a medium-size, heavy-bottomed saucepan, combine sugar, egg yolks and citrus mixture. Stir until sugar dissolves. Place over a low flame, stirring constantly, 10 to 12 minutes, until mixture thickens. Remove from heat; stir in butter, one piece at a time, until incorporated. Cool to room temperature; pour into tart crust or serving cups. Chill in the refrigerator several hours.
Presentation 1: Prim and Proper Tart
In a small saucepan over medium-low flame, heat jelly until just melted. In a large bowl, combine berries and toss very lightly with warm jelly. Place berries in circular rows around tart, leaving space between rows. Remove from tart pan and serve on a cake pedestal.
Presentation 2: Cookies and Citrus Crust
Any footed glass is well suited for this presentation. To each glass, add 1/2 cup fruit mixture, top with 1/3 cup citrus curd, and tuck a tart-crust cookie along the rim.