Serve them with a green salad to round out the meal.
Using a silicone brush, coat mushrooms all over with the oil mixture.
Place the mushrooms on a large rimmed baking sheet and bake until mostly soft, about 10 minutes.

Meanwhile, stir cheese, sour cream and all but 1 tablespoon scallions in a medium bowl.
Bake until the cheese is melted, about 5 minutes more.
Sprinkle with the reserved scallions.
Tips
Tip: To prepare portobello mushroom caps, gently twist off the stems of whole portobellos.
Using a spoon, scrape off the brown gills from the underside of the mushroom caps.
If you prefer, purchase portobello mushroom caps, rather than whole mushrooms.
- Daily Values (DVs) are the recommended amounts of nutrients to consume each day.
(-) Information is not currently available for this nutrient.