Step 1: Preheat the Oven

• Preheat your oven to 400°F (200°C). Grease a 9×13-inch baking dish or casserole dish with butter or non-stick spray and set it aside.

Step 2: Prepare the Cauliflower

• In a large pot of salted boiling water, blanch the cauliflower florets for about 5 minutes until they’re just tender but still firm. Drain well and set aside to cool slightly.

Step 3: Make the Pumpkin-Cream Sauce

• In a medium saucepan, melt the butter over medium heat. Add the minced garlic and sauté for 1-2 minutes until fragrant, being careful not to let it brown.
• Stir in the pumpkin puree, heavy cream, ground nutmeg, ground sage, salt, and pepper. Whisk together until smooth, allowing the mixture to simmer gently for 5-7 minutes until slightly thickened.

Step 4: Add the Cheese

• Remove the sauce from heat and stir in the shredded Gruyere cheese and Parmesan cheese. Continue stirring until the cheese has melted into the sauce, creating a rich and creamy mixture.

Step 5: Assemble the Gratin

• Place the blanched cauliflower florets in the greased baking dish. Pour the pumpkin-cream sauce evenly over the cauliflower, making sure every floret is coated in the creamy goodness.

Step 6: Prepare the Topping

• In a small bowl, combine the panko breadcrumbs, grated Parmesan cheese, olive oil, and fresh thyme. Mix until the breadcrumbs are evenly coated in the olive oil.
• Sprinkle the breadcrumb mixture evenly over the top of the cauliflower and sauce.

Step 7: Bake the Gratin

• Place the dish in the preheated oven and bake for 20-25 minutes, or until the topping is golden brown and the sauce is bubbling around the edges. The smell will be irresistible as the cheesy pumpkin sauce melds with the roasted cauliflower!

Step 8: Let it Rest

• Once baked, remove the gratin from the oven and let it rest for 5-10 minutes before serving. This helps the sauce set slightly, making it easier to serve.