Clean the mushrooms with a damp paper towel. Carefully remove the stems from the mushrooms and finely chop them.
Hollow out the mushroom caps a little more if necessary to create space for the filling.
Heat 2 tablespoons of olive oil in a pan over medium heat. Add the chopped mushroom stems, onions, and garlic. Sauté until the onions are translucent and the mushrooms have released moisture, about 5-7 minutes.
Remove from heat and stir in the breadcrumbs, Parmesan cheese, cream cheese, dried cranberries, chopped walnuts, thyme, pepper, and salt. Mix until everything is well combined.
Spoon the filling into the mushroom caps, pressing gently to fill them generously.
Place the stuffed mushrooms on a baking sheet or in a baking dish.
Drizzle a little olive oil over the tops of the mushrooms.
Bake in the oven for 20-25 minutes, or until the mushrooms are tender and the tops are golden brown.
Garnish with fresh parsley and serve warm as an appetizer or side dish.
Notes
Opt for large mushrooms like white button or cremini, which are easier to stuff and have a nice, meaty texture.
Panko breadcrumbs give a great texture, but regular breadcrumbs can also be used. You can also use gluten-free breadcrumbs if needed.
You can substitute it with sour cream or ricotta cheese if you don't have cream cheese.
Add ¼ teaspoon ground sage for a more festive flavor.
Press the filling into the mushroom caps firmly to ensure they hold together during baking. You can use a spoon or a small cookie scoop to help with this.
If you like a crispy topping, consider broiling the mushrooms for an additional 1-2 minutes at the end of baking, but watch them closely to avoid burning.
You can prepare the stuffed mushrooms a day in advance. Assemble them and store them in an airtight container in the refrigerator. Bake just before serving.