Preheat oven to 200C/400F and line a tray with parchment. Drizzle grapes with balsamic vinegar and oil and roast until soft (45 minutes to 1 hour, depends on how loose the bunch is).
Mix the flour and polenta together in a shallow bowl. Pat the feta dry in paper towels. Dip in the beaten egg and then the flour/polenta mixture. Heat a frypan on medium high heat and add oil. Fry the feta until golden on both sides (2 minutes or so). Serve with honey, rosemary, roasted grapes and bread.