Season the chicken with salt and pepper. In a large skillet, heat the EVOO, 2 turns of the pan, over medium-high heat. Add the chicken and cook, turning once, for 12 minutes. Transfer to a plate and cover with foil. Reserve the skillet.
Meanwhile, fill a medium saucepan with enough water to reach a depth of 2 inches; bring to a boil and salt it. Add the green beans and cook for 3 minutes, then add the asparagus and cook for 2 minutes; drain.
In another saucepan, bring 1 1/2 cups chicken broth, the milk and orange peel to a boil. Whisk in the polenta and cook for 2 minutes for a creamy consistency, whisking in a little more broth if needed. Whisk in 2 tablespoons butter and cover to keep warm.
In the reserved skillet, melt the remaining 2 tablespoons butter. Whisk in the flour and cook for 1 minute. Whisk in the vinegar, then the orange juice, then the remaining 1 cup chicken broth; simmer until slightly reduced, 2-3 minutes. Stir in any juices from the chicken; season with salt and pepper.
Slice the chicken thinly on an angle. To serve, mound the polenta in shallow bowls or onto plates and top with the asparagus, green beans and chicken. Drizzle the orange-balsamic sauce on top.