Preheat oven to 425° F (220 °C).

Lightly coat a 9 x 13-inch (23 x 33-cm) baking dish with spray; 
set aside.

To make tofu cream cheese, add tofu, nutritional yeast, miso paste, vinegar, oil, soy sauce, lemon juice, onion powder, garlic powder, and dill to a food processor; blend on high until smooth, scraping down sides, as needed. Add reserved tofu liquid, as needed, if mixture is too thick. Refrigerate half of tofu cream cheese for another recipe.

To make chicken, add remaining half of tofu cream cheese, spinach, artichoke hearts, and garlic to a medium mixing bowl; use a fork
to combine.

Slice 1 chicken breast approximately 3⁄4 of the way through, with knife parallel to cutting board; do not cut all the way through (chicken should open like a book). Use a scraping spatula to fill
as much spinach mixture as possible inside of chicken. Place in prepared baking dish. Repeat with remaining chicken breast. Spread remaining spinach mixture around chicken breasts. Lightly coat with spray; sprinkle with salt and pepper.

Bake for 35 minutes. Increase heat to 500° F (260 °C). Broil for
3 minutes, or until golden brown on top. Sprinkle with chili powder. Serve immediately.