Kohlrabi and Potato Gratin with Mustard-Cheddar Crust
Creamy layers of tender potato and crisp-kissed kohlrabi mingle with a tangy mustard-infused cream, then bake under a golden, crunchy cheddar-Panko topping for a satisfying mix of textures. The thinly sliced vegetables soften into silky ribbons while the crust delivers a toasty, savory finish and little pops of nutty cheese.
Swap in different melting cheeses or add aromatics to suit your pantry: use Gruyère or fontina for a more complex flavor, swap whole milk for 10% cream for a lighter dish, or fold in a handful of chopped thyme or rosemary with the cream. For gluten-free cooks, replace Panko with toasted crushed almonds or gluten-free breadcrumbs — the gratin will still brown beautifully.
Serve this gratin alongside roast meats, as a vegetable-forward main with a crisp green salad, or bring it to holiday gatherings as a seasonal side. It’s make-ahead friendly: assemble the day before and bake before serving, or reheat covered in a low oven until warmed through.
How to Make It
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1
Preheat the oven to 200°C (400°F). Butter a 23x30 cm (9x12 inch) baking dish or spray with oil.
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2
Thinly slice the kohlrabi and potatoes to 2–3 mm thickness using a mandoline or sharp knife. Thinly slice the onion and mince the garlic.
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3
Melt the butter in a medium saucepan over medium heat. Add the onion and cook until translucent, about 4 minutes. Stir in the garlic and cook 30 seconds more.
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4
Whisk the flour into the butter-onion mixture and cook 1 minute. Gradually whisk in the milk and cream until smooth. Bring to a gentle simmer and cook until slightly thickened, about 3–4 minutes.
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5
Remove the sauce from the heat and whisk in the Dijon mustard, nutmeg, 1 tsp salt, and 1/4 tsp pepper.
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6
Toss the sliced kohlrabi and potatoes in a large bowl with the remaining 1/4 tsp salt and 1/4 tsp pepper. Layer half of the potato and kohlrabi slices in the baking dish, overlapping slightly, then spoon half the cream sauce evenly over the layer.
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7
Repeat with the remaining vegetables and sauce so the dish is evenly layered. Press down gently to compress layers for even baking.
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8
Combine the grated cheddar, Panko, thyme leaves, and olive oil in a small bowl. Sprinkle the mixture evenly over the assembled gratin.
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9
Cover the dish tightly with foil and bake for 30 minutes. Remove the foil and bake uncovered until the top is golden and the vegetables are tender when pierced with a knife, about 12–15 minutes more.
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10
Let the gratin rest 10 minutes before serving to set. Serve warm as a seasonal side or a vegetarian main with a crisp salad.