1 tablespoon finely diced jalapeno pepper, seeded for mild, seeds intact for some heat
Kosher salt and freshly ground black pepper
1/3 cup roughly chopped cremini mushrooms
1 (10oz) package frozen, chopped spinach, thawed and squeezed of all water
½ lemon zested and juiced
1 tablespoon extra-virgin olive oil
2-3 tablespoons mayonnaise
2 tablespoons unsalted butter, at room temperature
4 (1/2”) slices sourdough bread
2 slice Swiss cheese
2 slice Provolone cheese
2 slice mild cheddar cheese
2 teaspoon roasted, unsalted sunflower seeds
Heat the olive oil in a medium non-stick skillet over medium heat.
Add the green onion, jalapeno and mushrooms. Cook for 3-5 minutes until lightly browned and softened.
Add the spinach and stir to break it up, spreading the spinach around the surface area of the pan. Season with salt and pepper.
Add the lemon juice and cook for 3-5 minutes until all the liquid has evaporated. Turn off the heat.
Add the lemon zest. Remove into a bowl and cool completely.
Once cooled, add 2 tablespoons mayonnaise and stir well to evenly incorporate throughout. Add another tablespoon of mayo if you prefer creamier. Set aside.
Heat a large, heavy, cast iron skillet over medium heat.
Spread the butter on all 4 slices of bread. Place buttered-side-down onto the hot cast iron pan. Lightly toast.
Add 1 slice of each cheese onto the bread slices still in the pan. Cook just until the cheeses are starting to melt. Remove 2 slices of bread and place onto a cooling rack to keep crispy (these are the sandwich bottoms).
Build the sandwich on a plate or cutting board. To do so, on the bottom slices of toasted bread, spoon 1/3 cup of the spinach-mushroom mixture. Sprinkle with sunflower seeds. Place the cheesy bread on top. Cut in half and serve.