Crispy Skillet Butternut Sage Lasagna with Brown Butter Fontina Step-by-step instructions

Before you start

Before starting, set the oven to 375°F (190°C) and line a baking sheet with parchment paper. Peel and seed the butternut squash, then slice it thinly using a sharp knife or mandoline. Grate the fontina and parmesan and keep them separate.

Pick the sage leaves from the stems and set aside a few extra for frying. Have the milk, butter, flour, salt, and pepper measured and ready, because the béchamel comes together quickly.

Instructions

Prepare the Squash and Cheese

1. 1Prep the squash and cheese
   Heat the oven to 375°F (190°C). Line a baking sheet with parchment paper. Peel the butternut squash, cut it in half lengthwise, scoop out the seeds, and slice it thinly, about 1/8-inch thick. Toss the slices with olive oil and a pinch of salt. Spread them in a single layer on the prepared sheet. Roast for 20–25 minutes, until just tender and lightly browned at the edges. Meanwhile, grate the fontina and parmesan on the large holes of a box grater. Set aside.
   Look for The squash is fork-tender and has golden spots; the cheese is shredded and ready.
   Tip Slice the squash uniformly so it cooks evenly. Use a mandoline if available.
2. 2Make the sage brown butter béchamel
   In a medium saucepan, melt the butter over medium heat. Add the sage leaves and cook, stirring occasionally, until the butter foams and turns golden brown and the sage is crisp, about 3–4 minutes. Remove the sage leaves with a slotted spoon and set them aside for the topping. Whisk the flour into the brown butter and cook for 1 minute. Slowly pour in the milk, whisking constantly, and bring to a simmer. Cook until the sauce thickens, about 5 minutes. Season with salt and pepper. Keep warm.
   Look for The sauce coats the back of a spoon and has a nutty aroma from the brown butter.
   Tip Whisk constantly when adding milk to avoid lumps. The sauce will thicken as it simmers.

At the end of this phase, the squash slices are fork-tender with lightly caramelized edges, and the cheeses are finely grated and ready. The béchamel is smooth, thick, and has a nutty aroma from the brown butter. The sage leaves are crisp and set aside for the topping.

Layer the Lasagna

3. 3Layer the lasagna in the skillet
   Spread a thin layer of béchamel on the bottom of a 10-inch cast-iron skillet. Arrange a layer of lasagna noodles, breaking them to fit. Add a layer of roasted squash, then a spoonful of béchamel, and a sprinkle of fontina and parmesan. Repeat the layers, ending with a final layer of noodles topped with the remaining béchamel and all the fontina and parmesan. Press down gently to compact the layers.
   Look for The skillet is full with distinct layers visible; the top is covered in cheese.
   Tip Break the noodles to fit the skillet without overlapping too much. Press gently to help them absorb sauce.

The skillet is filled with alternating layers of noodles, squash, béchamel, and cheese, ending with a generous topping of fontina and parmesan. The layers are compact and the top is evenly covered. The skillet feels heavy and full, with no exposed dry noodles.

Bake and Finish

4. 4Bake until golden and blistered
   Place the skillet in the oven and bake for 30–35 minutes, until the top is deep golden brown and the edges are bubbly and blistered. If the top browns too quickly, cover loosely with foil. Remove from the oven and let rest for 10 minutes before serving.
   Look for The cheese is browned in spots and the sauce is bubbling around the edges.
   Tip Letting it rest allows the layers to set and makes serving cleaner.
5. 5Fry the sage and serve
   In a small skillet, heat 2 tablespoons of olive oil over medium-high heat. Add the reserved sage leaves and fry until crisp, about 30 seconds per side. Drain on paper towels. Sprinkle the fried sage and extra grated parmesan over the lasagna. Pull a portion with a spoon to show the cheese stretch, and serve hot.
   Look for The sage leaves are crispy and the cheese pulls into long strands.
   Tip Fry the sage in batches if needed; they crisp quickly and can burn.

The lasagna emerges from the oven with a golden, blistered cheese crust and bubbling sauce at the edges. After a 10-minute rest, the layers hold together when sliced. The fried sage leaves are crisp and the extra parmesan adds a fresh, salty finish.

Common mistakes

A common mistake is slicing the squash too thick, which leaves it undercooked and crunchy in the final dish. Aim for even, thin slices and roast them until just tender.

Another pitfall is using pre-shredded cheese, which doesn’t melt as smoothly and can make the top greasy. Also, don’t skip the resting time—cutting into the lasagna right out of the oven causes it to fall apart.

How to tell it’s done

The lasagna is done when the top is deep golden brown with blistered spots and the sauce is bubbling up around the edges.

The internal temperature of the dish should be at least 165°F (74°C) to ensure everything is heated through, though there are no raw proteins to worry about.

Let it rest for 10 minutes after baking—this allows the layers to set, making it easier to serve and preventing the cheese from sliding off.