We are diving into chocolate this week on Tuesdays with Doire.  Marquise au Chocolat (page 357 in Baking Chez Moi) is a frozen chocolate mousse.   To make, melt 13 ounces bittersweet chocolate with 1/2 cup butter.  I used my microwave which I thought was easier than over simmering water. Beat 4 egg yolks, I used…