Using the smoothie attachment (A Magic Bullet would work) I added half the walnuts, lemon juice, maple syrup, apple cider vinegar, and a pinch of salt.
1 oz 28g walnuts, halved, 1 tablespoon lemon juice, 1 tablespoon maple syrup, 1 tablespoon apple cider vinegar, Pinch of kosher salt, 1 teaspoon stone-ground Dijon mustard