Step 1

Arrange a rack in the top third of the oven and heat the oven to 400°F. Remove 1 (4-ounce) package goat cheese from the refrigerator and let it warm up on the counter while you prepare the mushrooms and filling.

Step 2

Drain 1 (7-ounce) jar oil-packed sun-dried tomatoes well, pat dry with towels, and thinly slice if needed. Finely grate 1/2 ounce Parmesan cheese (about 1/4 cup).

Step 3

Finely chop 1 medium shallot. Remove the stems from 4 large portobello mushrooms and discard. Use a spoon to gently scrape out and discard the gills to make room for the filling.

Step 4

Brush the mushrooms on both sides with 2 tablespoons of the olive oil and season with 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Place the mushrooms on a rimmed baking sheet stem-side down and roast until just beginning to soften, about 10 minutes. Meanwhile, make the filling.

Step 5

Heat the remaining 1 tablespoon olive oil in a large skillet over medium heat until shimmering. Add the shallot and sauté until softened and translucent, 1 to 2 minutes. Add 5 ounces baby spinach (5 packed cups) and toss until just wilted, about 1 minute. Remove the pan from the heat. Crumble the goat cheese into the pan and stir until it just melts and coats the spinach. Stir in the sun-dried tomatoes.

Step 6

Remove the baking sheet from the oven and flip the mushrooms over with a flat spatula. Divide the spinach mixture evenly among the mushroom caps, then sprinkle with the Parmesan cheese.

Step 7

Roast until the mushrooms are tender and the cheese just starts to melts, about 10 minutes. Switch the broiler on and broil until the cheese browns, 2 to 3 minutes more.