Preheat oven to 400°F.

Sprinkle salt and then some pepper all over chicken. Heat 2 tablespoons of butter in a medium cast-iron skillet over medium-high. Nestle chicken, skin side down, in skillet in a single layer with no gaps (if you can’t quite fit them all, wait until chicken shrinks slightly, then puzzle in the remaining pieces).

Cook until meat is opaque around the edges and skin is deep golden brown, 6–8 minutes. Turn chicken skin side up and transfer skillet to oven; bake, uncovered, until chicken is cooked through, 10–15 minutes. Transfer chicken to a plate; cover loosely with foil to keep warm.

Set same skillet (with juices) over medium heat; combine chopped fennel bulb and leek in the skillet and sprinkle in some salt and pepper. Cook, tossing occasionally, until leek is looking golden around the edges, about 5 minutes. Add orzo and cook until pasta is darkened (it will take on a brown hue) to a nice nutty brown in spots and toasty smelling, about 3 minutes.

Pour in the wine and cook, stirring, until liquid is evaporated, about 1 minute. Add broth ½ cup at a time, stirring constantly and letting broth absorb before adding more, until orzo is tender and broth is mostly absorbed but pan is not dry, 10–15 minutes.

Remove the skillet from the heat, Taste and add more salt and pepper to your liking; mix in lemon juice and the remaining 1 tablespoon of butter; then add the chopped fennel fronds reserving a few to use as a garnish. Pile chicken on top and finish with the lemon zest and reserved fronds. Serve immediately.