
In a large serving bowl, combine the lemon juice, olive oil, garlic, mustard, maple syrup or honey, shallot (optional), salt, and pepper. Whisk to emulsify.
To the same bowl, add the snap peas, basil, and pistachios and toss to combine and coat with the dressing. Taste and adjust as needed.
Garnish with additional basil and pistachios and the red pepper flakes (optional). Serve right away.