Every week Recipe Monday features a brand-new recipe from one of our authors perfect for Meatless Monday.

This is a hearty, dinner party-worthy, visually arresting dish that’s well worth all the effort. I’ve adapted it from a recipe in Annie Somerville’s rightfully beloved vegetarian cookbook Fields of Greens—I cut the dairy back by half and swapped a few ingredients to accommodate what I had on hand the first time I made it. You should feel free to do the same, though I do find that this dish has exactly the right amount of richness for my palate. To feed a crowd, double the recipe and use an 13 x 18 sheet pan.

Serves 6 to 8

2 ten-ounce packages frozen chopped spinach
3 tablespoons olive oil, plus about 1/2 cup for brushing the filo
1 small white onion, diced
1-1/2 teaspoons herbes de provence
1 teaspoon salt
Freshly ground black pepper
5 garlic cloves, minced
12 ounces mushrooms (crimini, button, shiitake, or a combination), sliced
1/4 cup dry white wine
2 tablespoons roughly chopped parsley
8 ounces ricotta (about 1 cup)
2 eggs
1 one-pound package frozen filo sheets, thawed overnight in the refrigerator*
1 cup roughly chopped toasted walnuts
3 ounces feta, crumbled

*You’ll only use half the filo for this recipe.

1. Cook the spinach according to package instructions. Drain in a cheesecloth-lined colander and then, when cooled until safe to handle, wring out as much liquid as possible by gathering the spinach up in the cheesecloth and twisting.
2. Meanwhile, heat 1-1/2 tablespoons oil in a skillet over medium heat. Add the onion, 1/4 teaspoon salt, a few grinds of pepper, and 3/4 teaspoon of the herbes de provence. Cook until softened and translucent, 5 to 7 minutes, stirring occasionally. Add half the garlic and cook until fragrant, about 1 minute. Transfer the onion to a bowl and return the pan to the heat.
3. Turn the heat up slightly, to medium-high. Add 1-1/2 tablespoons oil to the skillet and then add the mushrooms, 1/4 teaspoon salt, a few grinds of pepper, and the remaining 3/4 teaspoon herbes de provence. Sauté the mushrooms until they release their juices and it begins to cook off, 7 to 9 minutes. Add the remaining garlic and stir until fragrant. Deglaze the pan with the white wine, scrape up the browned bits with a wooden spoon, and continue cooking until the pan is mostly dry. Transfer the mushrooms to the bowl with the onion. Add the parsley and stir to combine.
4. Crack the eggs into a mixing bowl and beat lightly. Add the ricotta, spinach, 1/2 teaspoon salt, and several grinds of black pepper, and whisk to combine.
5. Unfold the filo on a cutting board. Cut it in half so that you have two stacks of 9 x13-inch rectangles. Roll up one half, wrap tightly with plastic wrap, and put back in the freezer for another use. Drape a slightly damp tea towel or a few layers of paper towels over the remaining filo to keep it from getting brittle and drying out.
6. Preheat the oven to 375 °F.
7. Assemble the filo: Brush a thin layer of oil on the bottom and sides of a 9 x 13 baking dish. Lay in one sheet of filo, brush it lightly with some of the oil, then sprinkle with about a tablespoon of the walnuts. Repeat with 6 more layers of filo, sprinkling each layer with the walnuts, then lay one more sheet on top and brush with the oil. Spread the spinach-ricotta mixture over the filo, followed by the mushrooms and onions, and then the crumbled feta. Lay a sheet of filo over the fillings, brush it lightly with oil, then sprinkle with about a tablespoon of walnuts. Repeat with 6 more layers of oil, sprinkling each layer with the walnuts, then lay the final sheet over the top and brush generously with oil.
8. Refrigerate for 10 to 15 minutes, to chill the top layer. Then, using a long, sharp knife, cut the dish into 6 squares. Cut each square on the bias so that you end up with 12 triangles. Bake for 35 to 40 minutes, until crisp and golden. Serve hot.