Put walnuts, peeled garlic cloves, basil and mint in a blender. Blend on medium speed until you get a paste. While mixing, gradually add the olive oil, orange peel, salt and pepper.
Once the oil has been absorbed by the remaining ingredients, turn off the blender and try the pesto. If it is still too thick, add a little more olive oil and whisk for another 2 to 3 minutes.
This pesto goes well with green salads or spaghetti.