3 large eggs
1 cup whole milk
1 teaspoon sugar
1 1-pound challah loaf or brioche, cut crosswise into 12 slices (not including end pieces), each about 1/2 inch thick
3 1/2 tablespoons unsalted butter 

Berry sauce

3 cups blueberries
1/3 to 1/2 cup sugar (depending on sweetness of berries)
1 tablespoon fresh lemon juice
Confectioners sugar for garnish 

Preheat oven to 350 degrees. Wisk together eggs, milk, sugar and salt until blended.

Pour into a large baking pan and soak bread slices in 1 layer, turning once, for 8 minutes.

While bread is soaking, puree 1 1/2 cups berries with sugar and lemon juice in a blender. Transfer to a serving bowl and fold in remaining berries.

Heat 1/2 tablespoon butter in a 12-inch heavy skillet or griddle over moderately high heat until foam subsides. Transfer 4 soaked bread slices to skillet with a slotted spatula and cook until golden brown, about 1 minute on each side. 

Cook remaining bread in 2 batches, adding more butter as needed.     Transfer slices as cooked to a large shallow baking pan (using a clean spatula) and, when all are browned, bake in middle of oven until hot, about 5 minutes.

Serve with berry sauce. Dust with confectioners sugar.