Preheat oven to 375 °F. Place a pear half, flat-side up, into a baking dish and place on a baking tray. Brush pears with melted butter.
Pulse flour, brown sugar, sugar, cinnamon, nutmeg and salt to combine. Pulse in butter until a rough, crumbly texture. Pulse in oats and nuts just to combine. Pack crisp topping evenly over each pear and bake for 25 to 35 minutes, until pears yield when poked with a tester. Drizzle each pear with maple syrup and serve immediately.