Heat a large pot or dutch oven of medium-high heat. Add bacon once the pan is hot and cook until crispy, about 5 to 8 minutes. Remove the bacon with a slotted spoon to a paper towel lined plate to drain; set aside.

Add the chicken to the hot bacon grease in the pot. Cook the chicken until it is browned and no longer pink in the center, about 6 to 9 minutes. Remove the chicken to a bowl; set aside.

Add the onions to the pot and saute until softened and translucent, about 5 minutes. Add the rice to the onions and cook for 2 to 3 minutes to toast the rice.

Add 1/2 cup of stock to the rice. Stir often until the rice has completely soaked up the liquid. Repeat. Once the second liquid addition is absorbed, reduce the heat to medium. Continue adding 1/2 cup of broth at a time and stirring until the rice absorbs the liquid until the rice is al dente and slightly runnier than mashed potatoes. (You may not use all of the broth.) Each time you add liquid to the pot, it will take longer for the rice to soak up the broth. This is part of the cooking process. Don't crank up the heat to try to expedite things or your rice won't cook properly.

Add the Parmesan cheese and butter to the pot; stir until melted into the rice. Add the bacon and chicken back into the pot (including any juices in the chicken bowl), and season with salt and pepper to taste.

Add in the spinach and stir until the leaves have just wilted. Serve warm, topped with Parmesan if desired.