1. Preheat oven to 375 degrees.

2. Place squash on a baking sheet, cut-side up. Drizzle with olive oil and sprinkle with brown sugar; season with salt and pepper. Transfer to oven and roast until tender, about 40 minutes. Remove soft flesh from skin and transfer to the bowl of a food processor; process until smooth. You should have 4 cups of puree.

3. Transfer puree to the jar of a blender. Add egg yolk and cream; blend until well combined. Season with salt, pepper, and lemon juice.

4. Reduce oven temperature to 350 degrees. Divide squash mixture evenly between twelve 4-ounce ramekins. Set ramekins in a large baking dish; fill baking dish with enough hot water so that it comes one third of the way up the sides of the ramekins. Transfer baking dish to oven and bake until set, about 30 minutes.

5. Remove custards from water bath and let cool to room temperature. Serve garnished with quince, pine nuts, and pumpkin seeds.