Finely chop the cleaned and deveined shrimps on a cutting board or run it in a food processor or mixer. Mix the shrimps with finely chopped shiitake mushrooms.
Add in fish sauce, red pepper flakes and season with salt and pepper to taste. Mix well to combine all the ingredients.
Place one teaspoon of the shrimp filling in the center of the wonton wrapper. Use water to wet the edges of the wrapper with your finger and fold it in a triangle shape. Bring in two of the longer edges and give it a twist to form your wontons.
Steam the wontons in a bamboo steamer on medium heat for 15-18 minutes until the wontons are translucent.
Blend all the listed ingredients for the Pistachio Basil Pesto sauce and serve it along with the cooked wontons.