Step 1In a 10-inch nonstick skillet over medium-low heat, cook the pearl onions, red pearl onions, cipollini onions, baby turnips and baby carrots with one-fourth cup of the water, 2 tablespoons of the unsalted butter and 1 teaspoon sugar. Add salt and pepper to taste. Cook until all of the liquid has evaporated and the onions are nicely glazed. Remove from heat and cover tightly and keep warm until ready to serve.
Step 2When ready to serve, place the skillet back on low heat and add one tablespoon of butter and one tablespoon of water. Cook for a few minutes to reheat. Add the grapes and adjust the seasoning; cook an additional minute and keep warm.
Step 3Heat the roast chicken jus in a small saucepan. When the sauce is hot, swirl in a tablespoon of butter. Season the sauce to taste.
Step 4Warm a large serving dish. Cut the breasts into one-quarter-inch slices. Artfully arrange the chicken and vegetables on the warmed platter and spoon the sauce around the outside.