2 tablespoons unsalted butter, plus extra for buttering the dish
One 1-pound day-old loaf challah or white bread, unsliced
Two 6-ounce containers blueberries (about 2 1/4 cups)
6 large eggs
3 cups milk
1 1/4 cups heavy cream
2/3 cup plus 2 tablespoons granulated sugar
1/2 teaspoon pure almond extract
1/4 teaspoon kosher salt
One 16-ounce container strawberries, sliced
One 6-ounce container raspberries
1/2 teaspoon vanilla extract
Confectioners' sugar, for dusting, optional