Step 1: Prepare the Turnips
Peel and slice the turnips thinly (about ⅛ inch thick). To reduce bitterness, parboil the slices in salted water for 5 minutes, then drain and pat dry.

Step 2: Sauté the Aromatics
In a large skillet, heat butter and olive oil over medium heat. Add the chopped onion and cook until translucent, about 3–4 minutes. Stir in minced garlic and cook for another 30 seconds, just until fragrant.

Step 3: Make the Cream Sauce
Add the heavy cream and almond milk to the pan. Stir in salt, pepper, nutmeg, and thyme. Bring to a gentle simmer, then add half of the Gruyère and half of the cheddar cheese. Stir until melted and smooth.

Step 4: Assemble the Layers
Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish. Layer one-third of the turnips, spoon some sauce, and repeat for three layers. Top with remaining Gruyère, cheddar, and Parmesan.

Step 5: Bake Until Golden
Cover with foil and bake for 30 minutes. Remove foil and bake another 25–30 minutes until tender and golden brown. For extra crispiness, broil for 2–3 minutes.

Step 6: Rest and Serve
Let rest 10 minutes before serving. Garnish with fresh herbs if desired.