These are impressive tarts that are surprisingly easy to make.
Put the rolled oats in a food processor and process for about 30 seconds, until ground but not powdered. Add the flours, brown sugar, and salt and pulse until combined.
Add the butter and pulse until the butter pieces are small and the dough looks crumbly, like coarse sand. Add the milk and pulse for a few seconds.
Scoop the dough out of the food processor and form it into a large disk. Wrap tightly in plastic and refrigerate for at least 1 hour and up to 3 hours.
Dust a work surface with a sprinkling of flour. Unwrap the disk of chilled dough and put it directly on the work surface. Cut the dough into eight equal pieces, about 2 ounces each, and gently shape each piece into a smooth disk. The dough will be sticky. Make sure to turn the dough over (use a spatula or a bench knife) as needed and keep the working surface floured. Put the dough disks in the refrigerator for 10 minutes.
Using a rolling pin, roll each dough ball into a 6-inch round just over ⅛ inch thick. Place a round over a 4-inch tart pan and very gently press the dough into the pan. Roll the rolling pin over the pan to trim off excess. Repeat with the remaining dough rounds. Use any excess dough trimmings to make a ninth tart shell or freeze them for another time.
Put the tart pans in the freezer for 30 minutes.
Remove the tarts from the freezer, then arrange on a baking sheet and gently prick the dough with a fork.
Transfer the tart pans to wire racks and let cool completely.
Whisk the pudding one more time until smooth. Divide the pudding equally among the tart shells and sprinkle some of the crumbled candy bar over the pudding. Cover the tarts with plastic wrap and put them in the refrigerator for about 2 hours before serving.
The tarts can be stored, tightly covered, in the refrigerator for up to 2 days.
© 2008 All rights reserved. Published by Abrams Books.