This is from the December 2018 issue of a German Magazine lecker.de. This is our new "tuna casserole" go-to. Noodles are great but the potatoes add another level of texture.
Pressure cook unpeeled potatoes on high for 5 minutes with quick release when done.
Immediately put on a sheet pan and put in the fridge to cool.
Once the potatoes have cooled, peel them and slice them into 1/4" slices. I use a spam cutter that's like a giant egg slicer and don't separate the slices until I assemble. It cuts them all the same thickness and keeps them from oxidizing.
Set aside.
In a separate pan, boil 2 cups of water. Add the frozen spinach and cover. Cook for 6 minutes. Drain and squeeze out excess water. Season with salt and pepper, to taste. Set aside.
Saute onions in butter until they begin to look translucent. With pan on medium heat, sprinkle in the flour and stir until combined. Continue cooking for a few minutes to create a light roux. Add the milk all at once and whisk until smooth. Continue cooking for an additional three minutes or until mixture begins to thicken*. Remove the mixture from the heat.
* If it doesn't start to thicken, add a little cornstarch in water or extra flour. Be sure to continue cooking on low for a few minutes to cook out the raw flour taste.
Fold in the solid white tuna fish, breaking it into bite-sized chunks. Add the lemon zest and 1/2 of the cheese. Season with salt and pepper, to taste.
Preheat the oven to 350F.
Butter or spray a heavy 9" x 13" casserole or roasting pan that's at least 2 1/2" deep.
Spread a cup of the bechamel on the bottom of the casserole. Place 1/2 of the sliced potatoes in the pan.
Distribute 1/2 of the spinach and 1/3 of remaining cheese evenly across the layer.
Spread 1/2 of the bechamel as evenly as possible over the potatoes and spinach.
Repeat all three layers once more and top with the rest of the cheese.
Bake for 20-40 minutes until potatoes are soft and cheese on top is bubbly and golden brown.
Allow to rest for at least 25 minutes before cutting.
Servings 0