Put the flour, polenta, almonds or walnuts, brown sugar, and cinnamon in the bowl of a food processor. Pulse a couple of times to mix everything together.

Add the chilled butter pieces and pulse until the butter is finely broken up. Continue to pulse until the crispy topping no longer looks sandy is just beginning to hold together.

If you don’t have a food processor, chop the nuts finely with a chef’s knife then work the butter in with your hands or use a pastry blender.