Heat the oven to 375°F. Peel and core 6 Bartlett pears, then cut them into 48 irregular half-inch wedges. Work for 8 to 10 minutes so the cut fruit doesn’t sit exposed. Fold the wedges with lemon juice, dark brown sugar, cornstarch, cinnamon, cardamom, sea salt and vanilla using a rubber spatula in broad J-shaped motions. Scrape the bowl twice so no dry starch hides underneath. The wedges should look glossy with tiny cinnamon specks and no white cornstarch patches. You’ll smell lemon first, then warm cardamom as the sugar dampens. Stop folding after about 12 turns. More mixing bruises the fruit and releases extra juice. Letting the mixture stand beyond 15 minutes also creates a watery pool. Even wedges soften together, which prevents mushy edges and hard centers.

Keep 7 tablespoons of European-style unsalted butter near 40°F. Combine old-fashioned rolled oats, unbleached all-purpose flour, chopped English walnuts and light brown sugar for 1 minute. Then pinch in the butter for 3 to 4 minutes. Rub each cube between your fingertips and release it quickly. Shake the bowl once halfway through so dry crumbs rise from the bottom. The topping should hold loose clusters from pea-size to grape-size, while some dry oats remain visible. It should smell nutty but not greasy. (I tried soft butter once, the topping baked into one heavy sheet. Cold butter fixed it.) Stop if the butter reaches 65°F. Warm butter smears instead of forming pockets. Cold butter steams between crumbs, creating crisp pockets instead of a greasy sheet.

Melt 4 tablespoons of European-style unsalted butter over medium-low heat, about 4 on a 10-dial, for 2 minutes. Whisk in light brown sugar and heavy whipping cream. Keep the mixture at a steady simmer for 5 to 6 minutes. Scrape the bottom in slow figure-eight motions every 20 seconds. Stir in vanilla and fine sea salt during the final 30 seconds. The sauce will move from grainy beige bubbles to a smooth amber gloss. At 220°F, it should coat a spoon and leave a clean line when you swipe it. You’ll hear the bubbling soften as water evaporates. Remove it immediately. Going past 225°F makes the caramel overly thick and can split the fat. Stopping at 220°F keeps the caramel pourable after cooling.

Rub 1 tablespoon of softened European-style unsalted butter across a 9-inch square ceramic baking dish. Transfer the seasoned pears and spread them into an uneven two-layer bed. Work for 4 to 5 minutes while the oven stays at 375°F. Pour half the 220°F caramel in loose ribbons across the fruit. Scatter the chilled topping from 6 inches above, leaving several small pear gaps visible. The dish should look rustic, with 48 pear wedges overlapping at different angles and amber caramel peeking through. Keep topping clusters loose rather than pressing them flat. A compressed layer traps steam and turns dense. Reserve the remaining caramel for serving. If the dish sits longer than 10 minutes, the cold topping begins absorbing fruit juice. Loose layering lets steam escape, which protects the topping from sogginess.

Bake the assembled dish at 375°F for 35 to 40 minutes on the center rack. At minute 25, rotate the dish 180 degrees so the back edge doesn’t darken first. Don’t stir or cover the topping. Caramel Pear Crisp needs steady dry heat to brown the oats while the pears soften underneath. Start checking through the oven door at minute 34. The perimeter should bubble in slow glossy bursts, and the topping should turn deep golden with scattered walnut-brown patches. A thin knife should slide through a pear wedge with slight resistance. You’ll smell toasted oats before the center finishes. Go past 42 minutes and the walnuts can taste bitter. Pull it sooner and the starch stays loose. The 375°F heat thickens starch before the walnuts scorch.

Rest the baking dish for exactly 15 minutes, until the center falls near 140°F. Meanwhile, warm the reserved caramel over low heat, about 2 on a 10-dial, for 2 to 3 minutes. Spoon one-sixth of the crisp into a small white fluted ramekin. Add one 1/2-cup scoop of vanilla bean ice cream and drizzle 1 tablespoon of warm caramel in uneven ribbons. The portion should hold about 8 pear wedges with visible soft edges and distinct centers. The topping will crackle under the spoon while the ice cream begins melting at its base. Serve before minute 20 for the strongest hot-cold contrast. Skip the rest and fruit syrup floods the ramekin. Waiting longer than 30 minutes dulls the crisp texture. Resting lets starch finish setting, so each spoonful keeps distinct pear layers.