In a food processor, pulse the walnuts, garlic, and arugula together until everything is even processed. Drizzle in the olive oil through the feed tube while running the processor and stop once everything is creamy and combined into a thick, but spreadable paste.
Shrimp Flatbread
Preheat a grill pan to medium heat. Place the tortilla on the grill pan to warm through (about 30 seconds). Flip the tortilla and then add the pesto, spooning it out into an even layer over the tortilla.
Sprinkle on the shrimp, asparagus, and feta. Cover and allow to the ingredients to warm through (about 3-4 minutes at the most).