Gratin and France — Les Petites Gourmettes

Ingredients

• 6 tablespoons (3/4 stick) unsalted butter, divided
• 1 large onion, peeled and diced
• 2 pounds peeled and seeded butternut squash or pumpkin, cut into 1/4-inch cubes
• 1/4 teaspoon whole coriander seeds, crushed in a mortar or with the side of a chef’s knife
• Salt and freshly ground black pepper, to taste
• 1 tablespoon flour
• 1 cup milk
• 1/4 cup heavy cream
• 1 tablespoon fresh mint leaves
• 1/3 cup shredded Parmesan cheese
• 1/2 cup Panko crumbs