Preheat the oven to 350*F. Lightly butter a 10-inch cast iron skillet or any circle baking dish and set aside.
In a large bowl, gently toss together the sliced pears, maple syrup, vanilla, brown sugar, lemon juice, cornstarch, cinnamon, nutmeg, and salt until every slice is evenly coated.
Transfer the pear mixture to the prepared skillet or baking dish, spreading the mixture into an even layer.
In a separate bowl, combine the oats, flour, brown sugar, cinnamon, and salt.
Work the cold butter into the dry ingredients using a pastry cutter or your fingertips until coarse, and crumble clusters begin to form. Fold in the chopped pecans if using.
Scatter the crumble evenly over the pears without pressing it down.
Place in the oven and bake for 45-50 minutes, or until the topping is crisp and golden brown and the fruit filling is gently bubbling around the edges.
Allow the crisp to rest for about 15 minutes before serving so the filling has time to thicken slightly.
Notes
Tips for the Best Pear Crisp
Choose pears that are ripe but still slightly firm. Very soft, overripe pears can become mushy during baking.
Vanilla bean paste gives this dessert an especially rich vanilla flavor, but regular pure vanilla extract works well too.
Keep the butter cold until you’re ready to make the topping. Cold butter helps create those larger buttery crumbles that become wonderfully crisp in the oven.
Don’t overmix the topping. You want a mixture of smaller crumbs and larger buttery pieces rather than a completely uniform texture.
If your pears are especially juicy, add an additional teaspoon of cornstarch to the filling. You can also set the cast-iron skillet on a baking sheet to catch any juices that bubble over.
For even more crunch, sprinkle about a tablespoon of coarse sugar over the crumble before baking.
And be sure to let the finished pear crisp rest for at least 15 minutes. The filling will continue to thicken as it cools.
Storage: Store covered in the refrigerator for up to 4 days. Reheating: warm individual servings in the microwave for 30-45 seconds, or reheat the skillet in a 325*F oven until warmed through.Freezing: Freeze baked crisp for up to 3 months. Thaw overnight in the refrigerator before reheating.Make Ahead: Assemble the filling and topping separately up to one day ahead. Refrigerate both, then assemble just before baking for the freshest texture.