Heat the canola oil in a nonstick wok or large deep skillet over high heat.

Add the sliced napa cabbage and matchstick carrots to the hot oil.

Stir-fry the cabbage and carrots until they are crisp-tender, about 3 minutes.

Add the stemmed and sliced shiitake mushrooms, sliced scallions, and minced garlic to the wok.

Stir-fry the mixture until the vegetables are softened, about 4 minutes.

Add the hoisin sauce to the stir-fried vegetables.

Stir-fry until the hoisin sauce is heated through, about 30 seconds.

Top each low-carb flour tortilla with half of the stir-fried vegetable mixture.

Add 1 teaspoon of sour cream to each tortilla, if desired.

Roll up each tortilla to enclose the filling and serve immediately.