• Preheat the oven to 350℉ and lightly grease a 9x13 baking dish.

Prepare mushroom caps:

• Rinse the mushrooms quickly under the cold running water and pat them dry.
• Carefully pop the stems off each mushroom. (Food waste tip: you can sauté mushroom stems or add them to other veggies to sauté instead of discarding.)
• Create extra room in the mushroom: I like to scrape out the brown membrane (the gills) under the cap to create extra room in the mushroom cap for stuffing. Use a small spoon and gently scrape it out of each cap and discard.
  
• Toss each prepared mushroom cap with some oil, salt, and pepper and place into the baking dish to be stuffed.

Mushroom Stuffing:

• Combine the finely diced corned beef, squeezed sauerkraut, softened cream cheese, shredded Swiss cheese, Thousand Island dressing, and some salt and pepper in a mixing bowl. Use a spatula to mix everything together until evenly combined.
• Fill each mushroom cap generously with the Reuben mixture, stuffing it with a dome on top. Be generous with filling but not to the point that the dome is bigger than the mushroom.
  
• Sprinkle each stuffed mushroom cap with some Swiss cheese.
• Bake for about 30 minutes. Let the mushrooms rest a few minutes before transferring them into the serving platter.