Heat olive oil in a cast iron skillet over medium heat.

Sauté diced onion and garlic until tender. Remove from skillet and set aside.

Lightly salt and pepper chicken breasts and slice them into approximately 3/4-inch thick pieces at an angle.

Brown chicken pieces on each side and remove from heat. Chicken will be halfway cooked.

In the same skillet, add water with dissolved chicken bouillon cubes (or use chicken broth) and whisk in flour.

Add Riesling wine, sour cream, and Parmesan cheese to the skillet. Whisk until cheese melts and the sauce thickens.

Reduce heat to medium-low and add back the sautéed onions and garlic.

Add bite-sized vegetables (broccoli, sweet peppers, baby carrots, corn) to the broth.

Place the browned chicken back in the skillet, ensuring it is covered by the gravy mixture.

Reduce heat to low and simmer for 10-15 minutes, or until chicken is tender and cooked through.

Add leaf spinach (cut off stems) and cook for 1-2 minutes until spinach is tender.

Serve chicken and sauce over rice or small pasta.