Bring water to a boil in a large pot, about 5 minutes. Remove from heat and toss in rice noodles; wait 5 minutes. Stir and wait 5 minutes more. Drain and rinse in a colander.
Combine fish sauce, agave syrup, lime juice, and garlic in a bowl and set aside.
Heat 1 tablespoon coconut oil in a small omelet pan over low heat. Add egg and cook through without flipping, about 5 minutes. Set aside on a cutting board until cooled, about 15 minutes. Roll into a log and cut into thin strips. Set egg aside.
Heat 2 tablespoons coconut oil in a skillet over high heat. Add chicken, onion, and shallot and saute until fairly browned, 5 to 10 minutes. Add cabbage, carrots, and drained noodles; saute until well combined, about 5 minutes more.
Add fish sauce mixture, egg slices, basil, and sriracha sauce to the saute pan with the noodle mixture. Toss well, cover with a lid, and cook for 2 minutes.
Remove lid from saute pan and toss in peanuts. Serve in the pan or transfer to a large platter.
