Preheat your oven to 425 degrees Fahrenheit and line a baking sheet with parchment paper. Destem the mushrooms and add them to a bowl. Add 1 tbsp olive oil, ½ tsp salt, and ¼ tsp pepper, and toss to combine.
Step 2
Arrange the mushrooms on the baking sheet destemmed side up. Bake for 8-10 minutes. Discard any liquid, and set them aside to cool.
Step 3
While the mushrooms are baking, prepare the tapenade. Add the olives, garlic, Dijon mustard, parsley, ¼ cup olive oil, balsamic vinegar, and ½ tsp black pepper to your food processor. Pulse until the tapenade reaches your desired consistency. Taste and adjust the seasoning to your liking.
Step 4
Divide the tapenade among the baked mushroom pieces. Garnish with red pepper flakes on top. Serve immediately or keep in the fridge for later.