Preheat the oven to 375°F (190°C).
Lightly butter a 9-inch (23 cm) cast-iron skillet or a 9-inch (23 cm) round baking dish. Set aside.

For the crisp:
Place all the ingredients in a food processor and pulse for 1 minute, until the mixture forms large crumbs.

For the filling:
Mix all the ingredients in a large bowl.
Transfer the mixture to the prepared skillet or baking dish.
Top with the crisp mixture.
Bake for 40 to 45 minutes, or until the topping is golden brown and the filling is starting to bubble around the edges.
Let cool for 15 minutes before serving.