Preheat the oven to 375 degrees and line a baking sheet with parchment paper.
Place the basil, pine nuts, garlic, Parmesan, olive oil, salt, and black pepper in a food processor. Pulse until the mixture forms a coarse paste.
Transfer the pesto to a mixing bowl and stir in the cream cheese until fully combined.
Spoon the filling evenly into each mushroom cap and set them on the prepared baking sheet.
Bake for 18 to 20 minutes until the mushrooms soften and the filling looks set.