How to Make It
Set a fine sieve over a small bowl. Add 2 tablespoons of kosher salt, the five-spice powder and bouillon cube and rub them through the sieve. Set the chicken on a platter. Rub the spice blend all over the chicken inside and out and refrigerate it for 4 hours.
In a medium saucepan, combine the vinegar with the water, brown sugar and baking powder and cook over moderately high heat, stirring occasionally, until the sugar has dissolved. Transfer the syrup to a large bowl and let cool to room temperature. Stand the chicken in the syrup and ladle the syrup over it several times. Transfer the chicken to a rack set over a plate and refrigerate overnight. Bring to room temperature before cooking.
Pat the chicken dry inside and out with paper towels. In a large wok, heat 3 cups of the oil to 375° over moderately high heat. Carefully lower the chicken into the hot oil, breast side up, and cook until deeply browned on the bottom, about 20 minutes. Insert a large fork into the cavity and carefully transfer the chicken to a plate. Turn the chicken over and lower it into the hot oil, breast side down. Fry the chicken until deeply browned and cooked through, about 20 minutes longer.
Meanwhile, in a small skillet, toast the Szechwan peppercorns over moderate heat until fragrant, about 3 minutes. Transfer to a spice grinder and let cool. Add 3 tablespoons of kosher salt and grind to a fine powder.
Heat the remaining 1/4 cup of oil in a small skillet. Add the garlic and cook over low heat until golden, about 4 minutes. Transfer the garlic and oil to a small bowl.
Transfer the chicken to a carving board, breast side up, and let rest for 10 minutes. Carve and arrange the pieces on a platter. Scatter the garlic and oil all over the chicken and serve with the spiced salt.