Preheat the oven to 300 degrees F. Butter a 2-quart baking dish; set aside. Pulse the bread in a food processor until it is a mix of pea-size pieces and smaller crumbs. (You should have about 3 cups.) Spread the breadcrumbs on a baking sheet and bake, stirring halfway through, until dried and toasted, 30 to 40 minutes.
Meanwhile, melt the butter in a medium skillet over medium heat, stirring occasionally, until brown flecks appear, 5 to 6 minutes. Immediately transfer to a medium bowl. Toss the apples and strawberries with 1/2 cup sugar, the cinnamon and salt in a separate large bowl. Let sit until the sugar is dissolved and the mixture is juicy, about 10 minutes.
Increase the oven temperature to 375 degrees F. Stir the breadcrumbs into the browned butter, then scatter one-third of the breadcrumbs in the bottom of the prepared dish. Top with half of the fruit mixture. Repeat with the remaining breadcrumbs and fruit, ending with a layer of breadcrumbs. Sprinkle with the remaining 2 tablespoons sugar. Cover with foil and bake until the apples are almost tender and the filling is bubbling, about 1 hour 15 minutes.
Remove the foil and increase the oven temperature to 400 degrees F. Continue baking until the top is well browned and the apples are tender, 15 to 20 minutes. Let cool at least 15 minutes. Serve with whipped cream.