Preheat oven to 450°F with a rack in the lower third. Scrub 12 oz Yukon gold potatoes, halve lengthwise, and cut into ½-inch thick wedges. Toss on a rimmed baking sheet with 1 tablespoon olive oil and a generous pinch each of kosher salt and ground pepper. Roast on lower oven rack until lightly browned underneath, 12-15 minutes.

Thinly slice 1 large garlic clove. Halve and thinly slice all of the 1 red onion lengthwise into half-moons. Pick and finely chop 1½ teaspoons fresh oregano leaves; discard stems. Finely grate ½ oz Parmesan. Squeeze 1 tablespoon lemon juice into a liquid measuring cup. Add 1 packet chicken broth concentrate and ⅔ cup water to lemon juice; stir to combine. Cut any remaining lemon into wedges.

Sprinkle half of the Parmesan over roasted potatoes. Roast on lower oven rack until potatoes are golden brown and crisp underneath, 10-12 minutes.

Pat 12 oz boneless, skinless chicken breasts dry and pound to ½-inch thickness, if desired. Rub each breast with chopped oregano and season all over with salt and pepper. Heat 1 tablespoon olive oil in a medium skillet over medium-high. Add chicken and cook until browned and cooked through, 3-4 minutes per side. Transfer chicken to a plate.

Melt 2 tablespoons butter in the same skillet over medium-high heat. Add sliced garlic and onions; season with salt and pepper. Cook, stirring occasionally, until onions are softened and golden, 3-4 minutes. Add broth mixture, scraping up any browned bits from the bottom of the skillet. Bring to a boil. Meanwhile, pick and coarsely chop ¼ oz fresh parsley leaves; discard stems.

Add chicken, 5 oz peas, parsley, and remaining oregano to sauce. Simmer over medium-low until peas are warmed, 2-3 minutes. Transfer chicken to plates. Add potatoes to skillet, stirring to coat in sauce. Serve chicken with potatoes and peas, spooning lemon-herb sauce over top. Sprinkle with remaining Parmesan. Pass any lemon wedges for squeezing over. Enjoy!