In a medium bowl, mix the ground beef with the hoisin, peanut butter, soy sauce and sriracha by hand, until smooth. Form into 6 patties that are just larger than the buns. Refrigerate until ready to grill.
Preheat the grill to high heat. Slice all the veggies into thin even julienne-style pieces. Mix the soy sauce, sherry, black vinegar, garlic, ginger and Sriracha together in a small bowl. Whisk in the cornstarch and have another 1/2 cup of water ready on the side.
Grill the patties for 3-5 minutes per side. Remove from the grill and cover with foil.
Preheat a wok (or large skillet) on high heat. Add a scant amount of sesame oil, and stir fry the veggies in small batches for 30-60 seconds until just barely cooked and slightly charred. (You won't get char marks if you use too much oil or add all the veggies at once.) Turn off the heat and add the liquid mixture. Whisk to thicken. If the sauce is too thick, add a little water until you reach your preferred thickness. Mix in the stir fried veggies and peanuts.
Place a patty on each bun and top with stir-fried veggies. If you want even more kick, smear the buns with Wasabi Mayo. (1/2 cup mayo + 1 teaspoon wasabi paste)