Preheat the oven to 400°F (204°C). Grease two sheet pans and set aside. Then, remove the stems from the mushrooms and finely chop the mushroom stems.

On one sheet pan, toss the mushroom caps with the olive oil and a big pinch of salt. Place the mushrooms stem-side down and roast them for about 10 minutes, or until they release any extra water. Let them cool and then pat the mushrooms dry with paper towels.

Reduce the oven to 375°F (190°C). Then, melt 1 tablespoon (14 grams) of unsalted butter in a large skillet over medium heat. Add the Panko breadcrumbs and toast them until they're golden-brown, 1-2 minutes. Spoon the breadcrumbs into a small bowl and let them cool. Add the parmesan and toss to combine.

Melt the remaining 1 tablespoon (14 grams) of butter in the same skillet over medium heat. Add the chopped mushroom stems, shallots, and a big pinch of salt. Sauté until the shallots are golden-brown and the mushrooms are softened. Add more butter or olive oil to the pan, as needed. Spoon the veggie mixture into a medium mixing bowl and let the veggies cool slightly.

Once the veggies are cooled, add the boursin cheese, chives, and black pepper. Mix until smooth. Taste and add salt, if needed. Then, transfer the filling to a piping bag. Pipe the filling evenly between the cooled, roasted mushrooms.

Working one at a time, dip the top of each mushroom in the breadcrumb mixture, making sure to coat the cheese filling entirely. Line the mushrooms about 1-inch apart on the second prepared sheet pan. Bake the mushrooms for 12-15 minutes, or until the filling is hot and the breadcrumbs are toasty. Garnish with more chopped chives and enjoy!