Rinse the chicken thighs with cold water and pat them dry with paper towels. Season both sides with salt, pepper, and paprika. Transfer the chicken to a large bowl and add the lemon juice and parsley.
Heat a skillet and add a little oil. Pan-sear both sides of the chicken until nicely browned (but not cooked through). Remove the chicken and set aside. Add the remaining oil to the skillet and sauté the garlic and onions until the onions are slightly softened.
Add the potatoes, salt, and brown sugar, stirring to combine well. Transfer the chicken (along with any juices that have seeped out) into the skillet, arranging it between the potatoes and onions.
Bake the chicken and potatoes in the lower third of the oven for 30-40 minutes, or until the potatoes are cooked through. Serve immediately.
Notes
If the surface of the chicken gets too dark, cover it with aluminum sheet while baking.