Heat the oven to 200 C / 390 F. Place the squash chunks on a sheet pan lined with baking paper, drizzle with a little olive oil, and roast cut-side down for 35 to 40 minutes until the flesh is deep golden and very soft.

Remove from the oven and let cool for 10 minutes. Scoop the flesh into a fine-mesh sieve and press it through with a spoon, or blend until completely smooth in a food processor. You need 450 g of dry, smooth puree.

Butter four 180 ml ramekins generously with softened butter, making sure you cover the base and sides completely. Add about 3/4 tbsp of fine breadcrumbs to each ramekin and shake to coat evenly. Tap out any excess. Set aside.

In a large mixing bowl, combine the squash puree, drained ricotta, eggs, Parmigiano Reggiano, nutmeg, salt, and white pepper. Whisk until the mixture is smooth and fully combined. Taste and adjust salt.

Divide the mixture evenly among the prepared ramekins, filling each about three-quarters full. Tap each ramekin gently on the counter to settle the mixture and remove air pockets.

Place the filled ramekins in a deep roasting pan. Pour hot water from a kettle into the roasting pan until it reaches halfway up the sides of the ramekins.

Carefully transfer the pan to the oven and bake at 170 C / 340 F for 25 to 30 minutes, until the sformati are set at the edges but still have a very slight wobble at the center when you nudge the pan.

Remove the ramekins from the water bath and let them rest on the counter for 5 minutes before unmolding.

Run a thin knife around the inside edge of each ramekin. Place a warmed plate upside down over the ramekin, then flip both together in one confident motion. Tap the base of the ramekin and lift it away cleanly.

For the optional brown butter sauce, melt butter in a small pan over medium heat until it turns golden and smells nutty, about 3 minutes. Add sage leaves and fry for 30 seconds until crisp. Spoon over the unmolded sformati and serve immediately.