Preheat the oven to 180°C (350°F). Generously butter a 8x8 inch baking dish. I recommend using a ceramic dish.

If you haven’t already, peel and core the pears. Slice them into quarters, then chop into approximately 1.5 cm (⅔ inch) pieces.

Transfer the pears to a medium-sized bowl and toss them with the lemon juice and cornstarch, which will help thicken the juices. The recipe also works without cornstarch, though the filling may be slightly runnier.

Stir to combine, then spread the pear mixture evenly in the prepared baking dish.

In a separate bowl, combine flour, chopped walnuts, oats, brown sugar, and salt.

Add the cold butter cubes and use a fork or pastry cutter to work it into the dry ingredients until the mixture resembles coarse crumbs. It should hold together slightly when pinched.

Evenly scatter the crumble topping over the pears, breaking up any large clumps with your fingers.

Bake in the preheated oven for 40-45 minutes, or until the edges are bubbling and the topping is golden brown.

Serve: Let the crumble cool for a few minutes before serving. Enjoy it warm or at room temperature, perhaps with a scoop of vanilla ice cream or a dollop of whipped cream!