Caramelize the sugar in a saucepan over medium heat until golden brown. Deglaze with white wine vinegar, add onions and chilli and cook until the caramel has dissolved. Add grapes and simmer uncovered for 8 to 10 minutes. Mix in the walnut kernels. Salt, pepper and let cool.
Salt and pepper the venison medallions, fry in hot oil for 1/2 minute on each side. Then fry on each side for another 2 to 3 minutes on each side. Fry the bacon in a pan and serve with the grapes.