Preheat oven to 425 degrees.

Brush the mushroom caps with olive oil on both sides

Sprinkle with oregano and salt and pepper.

Roast in oven for 15 minutes, turn over and roast for an additional 15 minutes.

(While mushrooms are roasting, prepare the mashed cauliflower.)

For the mashed cauliflower, bring a large pot of water to a boil, add cauliflower florets. Cook for about 6 minutes, or until soft.

Once cauliflower is finished cooking, drain well, pat between several layers of paper towels until very dry. Place in a large mixing bowl.

Add butter and garlic.

With an immersion blender or potato masher, combine until creamy.

Season with salt & pepper and stir in fresh chives.

Spoon cauliflower mixture on to the Portobello mushroom and return to oven for 10 minutes or until cauliflower is lightly browned.