From "Slow Cooker Revolution," by the editors of America's Test Kitchen.
• 6 (12-oz.) bone-in, skin-on split chicken breasts, trimmed
• 3 tbsp. extra-virgin olive oil, divided
• 2 onions, minced
• 4 garlic cloves, minced and mashed to a paste, divided
• 1 tsp. minced fresh oregano, or 1 tsp. dried
•1/4 tsp. red pepper flakes
• 3 tbsp. flour
•1/2 c. dry white wine
• 11/2 lb. red potatoes (4 to 5 medium), scrubbed and cut into 1-in. chunks
• 1 c. chicken broth
• 1 fresh rosemary sprig
• 1 c. frozen peas
• 1/2 tsp. grated lemon zest plus 1 tbsp. fresh lemon juice
Dry chicken with paper towels and season with salt and pepper. Heat 1 tablespoon oil in 12-inch skillet over medium-high heat until just smoking. Add half of chicken, skin side down, and brown lightly, about 5 minutes; transfer to plate. Repeat with 1 tablespoon more oil and remaining chicken; transfer to plate. Let chicken cool slightly and discard skin.
Add onions, half of garlic, oregano and red pepper flakes to fat left in pan and cook over medium-high heat until onions are softened and lightly browned, 8 to 10 minutes. Stir in flour and cook for 1 minute. Slowly whisk in wine, scraping up any browned bits and smoothing out any lumps; transfer to slow cooker.
Microwave potatoes with remaining 1 tablespoon oil in covered bowl, stirring occasionally, until nearly tender, about 5 minutes; transfer to slow cooker. Stir broth into slow cooker. Nestle browned chicken with any accumulated juice into slow cooker. Cover and cook until chicken is tender, 4 to 6 hours on low.
Add rosemary sprig, cover, and cook on high until rosemary is fragrant, about 15 minutes. Transfer chicken and potatoes to serving platter and tent loosely with aluminum foil.
Let braising liquid settle for 5 minutes, then remove fat from surface using large spoon. Discard rosemary. Stir in peas and let sit until heated through, about 5 minutes. Stir in remaining garlic; lemon zest and lemon juice, and season with salt and pepper to taste. Spoon 1 cup sauce over chicken and serve with remaining sauce.