Trim excess fat from the chicken thighs and cut into bite-sized pieces.
Cut the zucchini, broccoli, carrot, mushrooms, red pepper, and onion into even-sized pieces similar to the chicken.
In a bowl, combine chicken broth, water, soy sauce, honey, and cornstarch; whisk until cornstarch is dissolved and set aside as the sauce.
Heat 1 Tbsp oil in a large skillet or wok over medium-high heat. Add the chicken in a single layer and cook, stirring occasionally, until browned and cooked through. Remove chicken and set aside.
Add the remaining 1 Tbsp oil and the butter to the skillet. Add broccoli, zucchini, mushrooms, red pepper, onion, and carrot; stir-fry until vegetables are crisp-tender, about 4–6 minutes.
Return the cooked chicken to the pan, add the minced garlic and ginger, and cook for about 1 minute, stirring constantly.
Add the cashews, then pour the prepared sauce into the skillet and bring to a boil. Reduce heat and simmer, stirring, until the sauce thickens and coats the ingredients, about 1–2 minutes.
Serve immediately. Garnish with green onion and sesame seeds if desired.
