Preheat the oven to 400 degrees F.
While the oven is preheating, make a batch of arugula pesto according to these directions and set aside. Remove stems from mushrooms, hollowing out the middle. Brush with olive oil and and place on a baking sheet.
Spoon or pipe in about 1-2 teaspoons of pesto in each mushroom. Top with 3-4 pine nuts and bake for 10 minutes.
Remove from oven and let cool 5 minutes before serving.
Serving and Storing - Serve immediately once assembled. Serve as an appetizer to your next holiday meal. Once assembled, this recipe doesn't store well. Only make as many as you plan on eating. Store leftover pesto in an airtight container in the refrigerator for up to 5 days.
Make in Advance - If you want to make this recipe in advance, feel free to prep the pesto several days before. The mushrooms can be prepped earlier in the day. When you are ready to serve, assemble, and bake.
Calories: 33kcal | Carbohydrates: 1g | Protein: 1g | Fat: 2g | Sodium: 4mg | Potassium: 162mg | Sugar: 1g | Calcium: 1mg | Iron: 0.2mg