Heat the olive oil in a dutch oven on medium-high heat. Add chopped onion and cubed chicken. Cook for about 5 minutes until the chicken starts to brown a bit and is no longer pink. Season with Italian seasoning, salt and pepper. Stir in garlic and cook for another 30 seconds until garlic gets aromatic.: You will smell the sweet, nutty aroma of softened onion and soon after, the savory, toasted notes as the chicken begins to brown, which signals Maillard flavors forming that deepen the whole dish. You should see small patches of golden color on the chicken , and the pan will give a gentle sizzle as the moisture evaporates. This initial sear seals juices and creates texture that keeps the chicken succulent after simmering. If the pan smoke rises quickly, lower the heat to avoid burning the aromatics. A common mistake is crowding the pot, which causes the chicken to steam rather than brown, so give pieces space and work in batches if necessary. When garlic becomes fragrant, which is quick, move on to the next step to prevent bitterness.
Add the rice, cream of chicken soup, chicken broth, milk and sour cream. Start with 2 cups of chicken broth and add more if needed until rice is fully cooked.: As you stir these creamy liquids into the pot, the mixture should become silky and slightly glossy, the rice absorbing the sauce and taking on flavor. You can see the liquid level change and the texture go from soupy to thicker, clinging to the rice like a blanket. This combination gives the casserole body and richness. Stir gently to distribute the rice and avoid breaking grains. A risk here is adding too much liquid at once, which can make the casserole soupy, so start with the suggested amount and reserve extra broth to adjust later if the rice needs more time.
Bring to a boil, then reduce heat, cover, and cook over medium heat until the rice is fully cooked, stirring occasionally, should take about 15-20 minutes.: When the pot reaches a lively boil you will see bubbling across the surface, then once covered it will settle into a low, steady simmer with occasional soft burbles. Listen for a faint percolating sound and watch the pot for steam escaping from the lid. As the rice swells, it will draw in the liquid and the mixture will thicken, which you can see around the edges. Stirring occasionally prevents sticking and helps you gauge doneness. Avoid lifting the lid too often, because heat loss extends cooking time. A common issue is undercooked centers in the rice , which means you may need to add a splash more hot broth and continue cooking for a few minutes.
Add the broccoli florets and half the cheese then continue cooking for 2 more minutes, until broccoli softens a bit. Sprinkle the remaining cheese on top and place the lid on the dutch oven for 3-4 minutes and let the cheese melt.: When you fold in the broccoli , the dish brightens visually with flecks of green, and a fresh vegetal scent appears. The residual heat and short additional cook time will soften the florets while keeping a slight bite. Incorporating half the cheddar cheese here melts into the sauce, making it glossy and cohesive. After sprinkling the remaining cheddar cheese on top, covering the pot traps heat and creates a gentle steam that melts the topping into a delightful, gooey layer. Be mindful not to overcook the broccoli , which becomes mushy and loses its color. If cheese does not fully melt, increase lid time by a minute or two rather than cranking up heat, which can make the cheese separate.
Remove from heat and let sit 2 minutes before serving.: After you take the pot off the burner, the casserole will settle and the flavors will knit together; you will notice the steam slow and aromas mellow into a harmonious whole. This brief rest allows the sauce to thicken slightly, so serving yields portions that hold their shape without being runny. Use this pause to taste and, if needed, adjust seasoning with a small pinch of salt or pepper. Rushing to serve right away risks a looser texture and hotter, less distinguishable flavors, so give those two minutes for the dish to reach its ideal consistency.
