Preparation

Oven-dry the bread:

• Heat the oven to 300°F. Slice the bread 3/4 inch thick. Spread the bread slices directly on the oven rack and bake until crisp all the way through (most of the moisture in the bread will be evaporated) and lightly browned, about 15 minutes.
• Cut the bread into 3/4-inch cubes (about 6 cups).

Roast the garlic:

• 将烤箱加热到350°F。将大蒜放入一个小的浅烤盘中，将植物油倒在上面，然后用箔纸盖住。烘烤，直到大蒜变成褐色和柔软为50至60分钟。冷静。从大蒜丁香中挑选或挤出果肉，然后在食品加工机中果肉果酱；您应该有大约1/3杯。可以提前制作泥，并冷藏直到准备使用。

煮洋葱：

• Heat the olive oil in a large nonstick skillet over high heat. When the oil is hot but not smoking, reduce the heat to medium and add the onions, salt, and pepper. Cook until the onions become soft and golden, 30 to 40 minutes. Add the vinegar and sugar; cook until the liquid is absorbed, about 3 min.; you should have about 1-1/2 cups. The onions can be made ahead of time and refrigerated until ready to use.

Make the pudding:

• 将烤箱加热到350°F。In a large bowl, whisk together the cream, eggs, egg yolks, roasted garlic, rosemary, salt, and pepper. Stir in the caramelized onions and the bread. Let sit for 30 minutes. to saturate the bread, stirring occasionally.
• Brush a 2-qt. (or 9×13-inch) baking dish evenly with the butter. Pour the bread mixture into the baking dish, distributing the ingredients evenly. Bake in the hot oven until lightly browned and firm, 40 to 45 minutes.