A weeknight gratin made loose in a pan, built around shredded Swiss that melts into crisp potatoes and onion. The starch in the potatoes thickens everything as it cooks, so you only need butter and heat to make it come together.

Serves 2. 35 minutes, 15 at the stove.

About 560 calories a serving, 21 g protein, 47 g carbohydrate, 34 g fat. From USDA figures for 100% of the ingredients; amounts are the recipe's.

Cook mode

1. Peel 1 pound of potatoes and slice them about a quarter inch thick, then slice 1 medium onion into thin half-moons. Melt 3 tablespoons butter in a 10-inch skillet over medium-high heat.
2. Add the onion to the butter, season with salt and pepper, and cook for about 2 minutes, stirring, until the onion softens slightly. Add the potato slices, toss them to coat in butter, season with salt and pepper again, and spread them in an even layer.2 min
3. Cook without stirring for 4 minutes until the bottoms start to brown. Stir and cook for another 4 minutes, undisturbed, until more browning happens.8 min
4. Scatter 1 cup of shredded Swiss cheese over the potatoes, cover the pan with a lid or foil, and lower the heat to medium. Cook for about 8 minutes, until the potatoes are tender when you poke them with a fork and the cheese has melted into creamy pockets.8 min
5. Taste and adjust seasoning with salt and pepper. Serve straight from the pan.

Note Swap aged cheddar for the Swiss. Leftovers keep three days covered in the fridge and warm well in a low oven. Serve with a green salad dressed with vinegar or a simple vegetable on the side to cut the richness.