Bring maple syrup, 1/4 cup chicken broth, 2 tablespoons kosher salt, black peppercorns, and garlic to a boil. Remove from heat; stir in cold water. Place chicken in a zip-top plastic bag; add brine. Seal; chill 2 hours. Remove chicken; discard brine. Sprinkle chicken with 1/4 teaspoon black pepper and 1/8 teaspoon kosher salt. Heat olive oil in a skillet over medium-high heat. Sauté chicken 5 minutes on each side or until done. Heat butter in a pan. Add Brussels sprouts and shallots; sauté 6 minutes. Stir in 1/4 cup chicken broth; cook 6 minutes. Stir in pecans.