Step 1: Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Step 2: Clean the portobello caps with a damp paper towel and gently scrape out the gills using a spoon.
Step 3: Heat 1 tablespoon of olive oil in a skillet over medium heat. Sauté the onion and garlic until soft, about 3-4 minutes.
Step 4: Add the chopped kale to the skillet and cook until wilted. Season with salt, pepper, and thyme.
Step 5: Remove from heat and stir in the cooked quinoa, pecans, and dried cranberries until well combined.
Step 6: Brush the outside of the mushroom caps with the remaining olive oil and place them gill-side up on the baking sheet.
Step 7: Spoon the filling into each mushroom cap, pressing down gently to pack it in.
Step 8: Roast in the oven for 20 minutes. If using cheese, sprinkle it on top during the last 5 minutes of baking.
Step 9: Remove from the oven and drizzle with balsamic glaze before serving.