INSTRUCTIONS
1. Adjust oven rack to lower-middle position and heat oven to 375 degrees. Combine garlic and oil in small saucepan. Cook, covered, over medium-low heat, stirring occasionally, until garlic is softened and straw-colored, 10 to 15 minutes. Reserve 1 tablespoon oil and transfer remaining garlic mixture to food processor; puree until smooth. Let cool.
2. Pat chicken dry inside and out with paper towels. Combine ¼ cup garlic puree, ¼ teaspoon salt, and ½ teaspoon pepper in small bowl. Tuck wings behind back, then, following photos 1 and 2 at left, spread garlic mixture under skin of chicken and rub reserved oil over outside of chicken. Tie legs together with kitchen twine. Season chicken with salt and pepper and arrange, breast-side down, on V-rack set inside roasting pan. Roast until just golden, about 35 minutes.
3. Remove chicken from oven and, using wad of paper towels, flip chicken breast-side up. Raise oven temperature to 450 degrees. Whisk broth, wine, ½ cup water, and remaining garlic puree in measuring cup, then pour into roasting pan. Return chicken to oven and roast until thigh meat registers 170 to 175 degrees, 30 to 40 minutes. Transfer chicken to cutting board and let rest 20 minutes.
4. Meanwhile, transfer pan juices and any accumulated chicken juices to saucepan; skim fat. Whisk remaining water and cornstarch in small bowl, then add to saucepan. Simmer until sauce is slightly thickened, about 2 minutes. Whisk in butter, then strain into serving bowl. Stir in tarragon and season with salt and pepper. Carve chicken and serve, passing sauce at table.
