Cook rice following package directions. Set aside. Cover to keep warm. While rice is cooking, make veggie mixture.
Rinse and chop broccoli and celery. Peel, rinse, and chop carrots. Rinse and mince jalapeño. Peel and finely chop garlic.
If using chicken, remove any skin. Cut chicken into small pieces.
In a small bowl, stir together soy sauce, brown sugar, and cornstarch. Add 1 teaspoon of the minced jalapeño. Stir.
In a medium skillet over medium-high heat, heat oil. Add ground ginger and stir. Add chicken or tofu. Cook, stirring occasionally, until slightly browned and starting to cook through, about 2 minutes.
Add chopped veggies. Stir frequently. Cook until veggies are tender and chicken is completely cooked but not dry, about 5–7 minutes.
Add soy sauce mixture. Bring to a boil. Reduce heat. Simmer until sauce is slightly thickened, about 2 minutes.
Serve over warm brown rice.