Dry the shrimp with paper towels (Make sure they've been thawed, peeled, and deveined).
Heat about 2 tbsp of oil over medium heat in a large pan. Add the onions and saute for 1-2 minutes. Next, add the asparagus and continue cooking and strirring 3-4 minutes until slightly softened (but not too much).
Lower the heat to medium. Add the shrimp to the vegetable mixture and cook for 2-3 minutes.
Add the coconut milk (reserving 2 tbsp for later) and spices (save the arrowroot starch for later). Stir until everyting is evenly combined.
Mix 1-2 tbsp remaining coconut milk with the arrowroot starch, then add to the pan with the other ingredients. Stir in and turn heat to low. Simmer for 3-4 minutes on low to allow the mixture to thicken.
Stir in the spinach and allow to wilt; about 2 minutes.