To make the sauce, whisk together broth, hoisin, cornstarch, soy sauce, and sesame oil.
Heat 2 teaspoons vegetable oil over medium-high heat in a wok or nonstick skillet.
Add the firm vegetables, such as celery and carrots, and cook 2 to 3 minutes.
Add the tender vegetables and cook 2 minutes more.
Push the vegetables to the side and add the remaining 1 teaspoon vegetable oil to the center of the skillet.
Add the garlic and ginger and cook 30 seconds, or until fragrant. Stir into the vegetables.
Give the sauce a stir (to mix in any cornstarch that has settled), and pour it over the vegetables.
Let simmer one minute, or until the sauce has thickened.
Garnish with sesame seeds if desired.
