Preheat the broiler with a rack 4-5 inches from the heating element. Line a small sheet pan with foil. Cut the bell peppers in half through the stem end and place the peppers cut side down on the pan. Broil until blackened all over. Alternatively, the peppers can be blackened directly on the flame of a gas stove; turn them often for even cooking (just let them burn; they should be evenly blackened). Transfer the peppers to a bowl and cover with plastic wrap to steam for 5-10 minutes. Peel off and discard the skin. Rinse the peppers briefly to remove most of the blackened bits. Discard the stems and seeds and coarsely chop the peppers.

In a food processor with the blade running, add the garlic cloves and coarsely chop. Add the roasted red peppers, pine nuts, basil (or basil and mint), Parmesan cheese, red pepper flakes (if using), lemon juice and a generous pinch of salt and pepper. Process until mostly smooth. With the blade running, drizzle in 1-2 tablespoons of extra virgin olive oil, until you reach the consistency you want (I usually use 2 tablespoons). Taste and season with additional salt, pepper and/or lemon juice as needed. Do Ahead: The pesto can be covered and refrigerated for up to 3 days.