Pat the chicken thighs dry and season with salt, pepper, garlic powder, and smoked paprika.
Heat olive oil in a large deep skillet over medium-high heat. Add the chicken and cook until browned and cooked through, about 5 to 6 minutes per side. Transfer to a plate.
Reduce heat to medium and melt butter in the skillet. Add leeks and cook until softened, about 4 minutes. Stir in ground coriander, red pepper flakes, and minced garlic, and cook until fragrant, about 30 seconds.
Add pearl couscous and cook, stirring, for 1 minute to lightly toast it. Pour in white wine and cook until mostly reduced.
Add chicken broth and bring to a simmer. Stir, then nestle the chicken back into the skillet. Cover and cook over medium-low heat until couscous is tender and most of the liquid is absorbed, about 10 to 12 minutes.
Stir in peas, lemon zest, lemon juice, and chopped dill or parsley. If using Parmesan, stir in ½ cup and add more to taste. If using feta or goat cheese, crumble it over the top before serving. Add a splash more broth if desired.
Taste and season with more salt, pepper, and lemon juice as needed. Finish with more herbs and cheese before serving.
