Preheat oven to 425°F with racks in upper and lower thirds.
Cook onion and bell pepper in 3 tablespoons oil in a 12-inch heavy skillet over medium heat, stirring occasionally, until softened and golden, about 15 minutes. Add garlic and cook, stirring frequently, 2 minutes.
While onion mixture cooks, rinse matzo farfel in a colander under warm running water until softened, 30 seconds to 1 minute. Drain, pressing gently to extract excess water.
Remove onion mixture from heat and stir in farfel, pistachios, raisins, parsley, 3/4 teaspoon salt, and 1/2 teaspoon pepper. Whisk together eggs and 3/4 cup broth, then stir into farfel mixture.
Set aside 1 1/2 cups stuffing and transfer remainder to a generously oiled 1 1/2-quart shallow baking dish.
Bake stuffing in dish in lower third of oven until set and golden, about 30 minutes.
While stuffing bakes, stir together spices with 1 teaspoon salt and 1/2 teaspoon pepper in a large bowl.
Insert a paring knife horizontally into middle of thicker end of each chicken breast half, stopping about 1 inch from opposite end, then open incision with your finger to create a 1-inch-wide pocket. Pack 3 tablespoons stuffing into each pocket. Pat chicken dry and add to spices, tossing to coat.
Straddle a large flameproof roasting pan across 2 burners, then add remaining 3 tablespoons oil and heat over medium-high heat until it shimmers. Sear chicken, skin side down, until skin is deep golden, about 5 minutes. Turn chicken over, then roast in upper third of oven until just cooked through, 16 to 20 minutes.
Transfer chicken to a platter and straddle roasting pan across 2 burners, then add wine and deglaze by boiling, stirring and scraping up brown bits, 1 minute. Stir in 3/4 cup broth. Whisk together remaining 1/4 cup broth and potato starch and whisk into sauce, then cook, whisking, until slightly thickened, about 2 minutes. Strain sauce through a fine-mesh sieve into a measuring cup. Let stand until fat rises to top, 1 to 2 minutes, then skim off and discard fat (or use a fat separator). Season sauce with salt.
