Wash and dry the baby bok choy, then slice it in half and remove any loose outer layers. (If desired, you can chop the leaves off of the tough stem and roughly chop them, which makes it easier to eat.) Slice the mushrooms and peel and slice the carrots. Peel and slice the garlic, and set it aside.
Prepare a small bowl with the orange juice, soy sauce and rice vinegar. In another small bowl, mix the cornstarch with 1 1/2 tablespoons water until dissolved.
Heat the sesame oil in a large skillet over medium high heat. Add the mushrooms and carrots and cook for 5 minutes, stirring occasionally until browned. Move the vegetables to the side to make space for the bok choy.
Add baby bok choy cut side down, 2 tablespoons water, and a few pinches of kosher salt and cook for 2 to 3 minutes until bright green and just tender, stirring occasionally and turning the bok choy once.
Add sliced garlic and cook for 30 seconds.
Reduce the heat to medium. Add the orange juice, soy sauce, and rice vinegar and stir to combine. Immediately drizzle in the cornstarch slurry, stirring constantly. Keep cooking about 1 minute until sauce thickens. Sprinkle with 1 pinch salt and serve immediately. When eating, cut off the bok choy leaves from the stem with a knife and fork. Serve with noodles or a protein (like baked tofu, chicken or shrimp).