Prepare the chicken thighs:
Heat olive oil in a large oven-safe skillet over medium-high heat. Season the chicken thighs with salt and pepper on both sides. Once the oil is hot, add the chicken thighs, skin-side down, and cook for 5-7 minutes until the skin is crispy and golden brown. Flip the chicken over and cook for an additional 5 minutes. Remove the chicken thighs from the skillet and set them aside.

Sauté the garlic and lemon:
In the same skillet, add 1 tablespoon of butter. Add the minced garlic (reserving 1 clove) and sauté for 30 seconds until fragrant. Add the lemon slices and cook for another 2 minutes, letting them caramelize slightly.

Cook the orzo:
Add the orzo to the skillet and stir it around in the garlic and lemon mixture for a minute. Pour in the chicken broth and lemon juice. Stir to combine, then bring the mixture to a simmer.

Return the chicken to the pan:
Place the chicken thighs on top of the orzo in the skillet. Add the remaining tablespoon of butter to the pan. Cover the skillet with a lid and transfer it to a preheated 375°F (190°C) oven. Bake for 25-30 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).

Finish the dish:
Remove the skillet from the oven. Stir in the baby spinach and allow it to wilt. Sprinkle the freshly shredded parmesan cheese over the top, stirring gently until melted. Taste and adjust seasoning with salt and pepper if necessary.

Serve and garnish:
Garnish with fresh parsley and additional lemon slices if desired. Serve the chicken thighs with orzo and a spoonful of the pan sauce.