Creamy Tuna Potato Gratin

1.Preheat your oven to 375°F (190°C).

2.In a large pot, bring salted water to a boil and add the sliced potatoes. Cook for about 5-7 minutes until just tender. Drain and set aside.

3.In a saucepan over medium heat, melt the butter. Add the chopped onion and garlic, sautéing until the onion is translucent.

4.Stir in the flour, cooking for about 1 minute until it forms a paste. Gradually whisk in the milk, ensuring there are no lumps. Continue to cook until the sauce thickens, about 5-7 minutes.

5.Add the Dijon mustard, dried thyme, dried oregano, salt, and pepper to the béchamel sauce. Stir in half of the shredded cheddar cheese until melted and combined.

6.In a large baking dish, layer half of the cooked potatoes at the bottom. Spread half of the flaked tuna over the potatoes, followed by half of the diced tomatoes. Pour half of the béchamel sauce over this layer.

7.Repeat the layers with the remaining potatoes, tuna, tomatoes, and béchamel sauce. Top with the remaining cheddar cheese and sprinkle breadcrumbs evenly over the top.

8.Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 15-20 minutes until the top is golden and bubbly.

9.Allow the gratin to cool for a few minutes before serving.