Preheat the oven. Heat the oven to 190°C (375°F). Lightly butter the 9×13-inch baking dish so the filling does not stick.

Slice the apples. Peel, core and slice the apples into slices about 5 mm thick. Thin slices turn tender in the bake without going mushy — thick chunks stay hard in the middle.

Toss the filling. In a large bowl, toss the apple slices with the granulated sugar, flour, lemon juice, cinnamon, nutmeg and salt until every slice is coated. The flour thickens the juices as the crisp bakes, and the lemon keeps the apples bright.

Make the topping. In a medium bowl, whisk together the flour, oats, brown sugar, cinnamon and salt. Add the cold cubed butter and rub it in with your fingertips — or cut it in with a fork — until the mixture forms pea-sized clumps. Cold butter is the secret to a crisp topping; melted butter makes it greasy.

Assemble. Spread the apple filling evenly in the buttered dish, then sprinkle the topping over it in an even layer, right to the edges. Do not press it down — a loose topping bakes up crunchier.

Bake. Bake for 40–45 minutes, until the filling is bubbling around the edges and the topping is deep golden and crisp. If the top browns too fast, cover it loosely with foil for the last 10 minutes.

Rest. Let the crisp rest for 10 minutes before serving — the filling thickens as it cools a little, and the topping stays crisp. Serve it warm, not piping hot.

Serve. Spoon the warm crisp into bowls and top with vanilla ice cream or whipped cream. The contrast of warm crisp and cold cream is the whole dessert.