Cheesy vegan udon noodles with Brussels sprouts

Name: Cheesy vegan udon noodles with Brussels sprouts
Ingredients: 2 (250 gram pouches) frozen udon noodles; 2 teaspoons avocado oil (or other neutral flavored oil, divided); 1/2 cup chopped onions; 2 cloves garlic (minced); 2 cups thinly sliced Brussels sprouts; Pinch of salt; 1/2 cup water (+ more or boiling udon noodles); 2 teaspoons white miso paste; 1/4 cup raw cashew pieces**; 1/4 cup + 1 Tablespoon nutritional yeast flakes; 1 teaspoon tamari; 1/2 teaspoon sriracha (+ more for drizzling on top); Chili crisp (optional garnish)