In a shallow bowl, mix 3 tablespoons flour, 1 teaspoon salt, 1/2 teaspoon pepper, and 1/2 teaspoon garlic powder. Dredge each chicken thigh in the mixture, pressing to coat and shaking off any excess.

Heat 2 tablespoons olive oil in a large skillet over medium-high heat until shimmering. Add chicken thighs in a single layer (work in batches if the skillet is crowded) and cook 2–3 minutes per side, until golden brown. Transfer browned chicken to a plate.

Reduce heat to medium. Add 6 pressed garlic cloves to the skillet and cook, stirring, about 30 seconds (do not let the garlic burn).

Pour in 1/3 cup balsamic vinegar, 1/4 cup chicken broth, and 3 tablespoons honey. Stir and scrape the browned bits from the bottom of the skillet to incorporate into the sauce.

Add the 2 diced Roma tomatoes to the skillet and bring the sauce to a brief boil.

Return the chicken thighs to the skillet, nestle them into the sauce, cover, reduce the heat to low, and simmer for 3–4 minutes.

Add 3 cups fresh baby spinach, recover, and cook 2–3 minutes more, until the spinach is wilted and the chicken reaches an internal temperature of 165°F. If the chicken hasn’t reached 165°F, continue to simmer a few more minutes and recheck.

Remove from heat, spoon sauce over the chicken, and sprinkle with shaved Parmesan cheese before serving.