Cut open and peel the roasted butternut squash. If baked whole, scoop out the seeds and fibers first.
Place the pulp in a large bowl and process into a winter squash puree using a potato masher for a rustic texture or a food processor for a silky finish.
Heat 3 tbsp (45ml / 42g / 1.48 oz) of the butter in a 12-inch (30cm) nonstick frying pan over moderate heat until it is hot and frothing.
Add the crushed fennel seeds, cardamom seeds, and minced green chilies to the butter, stirring for just a few seconds until fragrant.
While the squash cooks, toast the 0. 25 cup (25g / 0.88 oz) of shredded coconut or hazelnuts in a 300°F (150°C) oven until golden brown.
Before serving, garnish the dish with the toasted coconut/hazelnuts, the remaining 1 tbsp (15ml / 14g / 0.49 oz) of butter, and a fresh sprinkle of lime juice.
Don't Burn the Spices: When tempering the fennel and cardamom seeds in butter, only let them sizzle for 15–30 seconds. They should be fragrant, not brown; burnt spices will make the Kaddu Bharta taste bitter.