Sear the duck breast (6 minutes on the skin side and 4 minutes on the other side). Set aside.
Heat the milk with the butter. When it begins to boil, remove from the heat and slowly pour in the polenta. Stir and cook until smooth. Spread the polenta on a board. When cooled, cut out circles using a biscuit cutter and then sear both sides.
In a saucepan, combine the wine, orange slices, cinnamon stick, lemon slices and clove. Bring to a boil, remove from the heat and let steep for 1 hour. Strain the infused wine and return it to the saucepan. Simmer until the sangria sauce is reduced, then add the duck stock.
Cut the peach in half, remove the skin and sear both sides in a pan with some butter.
To serve, place a polenta circle on the plate and top it with the peach and half of the duck breast, sliced. Drizzle everything with the sangria reduction.