Cook rice, if using, and keep warm.
In a large skillet or wok, heat sesame oil, garlic, ginger and pepper flakes on medium high heat, 30 seconds.
Add bell pepper, onion and snap peas and stir to coat with oil. Cook, stirring occasionally until the veggies are slightly softened, 3 to 4 minutes.
Add the shrimp and stir or toss until the shrimp is cooked through, 3 to 4 minutes. The shrimp will be totally pink when done.
While the vegetables are cooking, mix the sauce ingredients in a sauce pan on medium heat and cook, stirring, until thickened, about 1 to 2 minutes.
Remove the shrimp skillet from the heat and pour 1/2 of the sauce on the shrimp and vegetables and stir to coat, reserving the remainder for plated dishes.
Serve the shrimp over a bed of rice, and top with chopped peanuts, and green onion.
Add additional sauce if desired.