Pat the chicken thighs dry and season generously with kosher salt and freshly ground pepper.
In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Carefully place the chicken thighs skin side down in the hot oil and brown them for 4-5 minutes on each side, until the skin is crispy and golden. The chicken thighs do not need to be fully cooked at this point. Remove the thighs from the skillet and set them aside.
Add the remaining 2 tablespoons of olive oil to the skillet and sauté the diced onion until it starts to soften. Then, add the orzo and toast it over medium-high heat for 3-4 minutes. Add the minced garlic and cook for another 1-2 minutes, stirring constantly to prevent the garlic from burning.
Pour the chicken broth into the skillet and use a silicone spatula or wooden spoon to deglaze the pan, scraping up any browned bits. Bring the broth to a boil, then return the chicken thighs to the skillet. Reduce the heat to medium-low, cover, and let simmer for 8 minutes.
After 8 minutes, layer the broccoli florets over the chicken and orzo, then cover the skillet again. Continue cooking for another 12 minutes, or until the chicken thighs reach an internal temperature of 165°F (74°C) and the broccoli is tender.
Remove the chicken thighs from the skillet and stir the orzo and broccoli together with the shredded cheddar cheese. Taste and season with additional salt and pepper as needed.