1. Let chicken stand at room temperature for 20 minutes. Sprinkle chicken with 1/4 teaspoon pepper and 1/4 teaspoon salt. Heat a large stainless steel skillet over medium-high heat. Add 1 tablespoon oil; swirl to coat. Add chicken to pan, rounded side down; cook 5 minutes. Turn chicken over; reduce heat to medium, and cook 5 minutes or until done. Remove chicken from pan; let stand 5 minutes.
2. Add remaining 1 teaspoon oil, onion, and garlic to pan; sauté 1 minute. Add flour; sauté 30 seconds. Add wine to pan; cook 30 seconds or until liquid almost evaporates, stirring constantly. Stir in stock; bring to a boil, scraping pan to loosen browned bits. Reduce heat to medium-low; simmer 3 minutes or until reduced to 1/2 cup, stirring occasionally. Remove pan from heat; stir in remaining 1/4 teaspoon pepper, remaining 1/8 teaspoon salt, butter, and sugar. Sprinkle with parsley.