1. In a small saucepan, warm the prunes with the liquor over moderate heat, stirring them a few times while cooking, until most of the liquid is absorbed. Cover, and remove from heat and let cool. (The prunes can be done a day or two before using.)
2. To make the custard, put the milk, eggs, yolks, sugar, melted butter, vanilla, salt, and flour in a blender. Blend until smooth. Refrigerate the custard for at least four hours, or overnight.
3. To bake the Far Breton, preheat the oven to 400ºF (200ºC).
4. Generously butter the bottom and sides of a baking dish roughly 10-inches (25-30cm) in length, or a round cake pan 10 inches in diameter. Do not use a springform pan which will leak. Dust with flour and tap out the excess. Place the prunes in the bottom of the baking dish.
5. Stir the chilled custard a few times, then pour it over the prunes and bake until the top is gently browned, 45 to 50 minutes. Let cool completely, then slice into bars.

Storage:

Far Breton can be made up to three days before serving and refrigerated. Let come to room temperature before serving.