Pre-heat the oven to 220oC, 425oF, Gas Mark 7.
Cut the veal into 8 equal slices and bash gently with a rolling pin to flatten until they are thin, like rashers of bacon. Place a slice of prosciutto, the chopped sage, lemon zest and a little seasoning on 4 of the pieces of veal. Put the other pieces on top to create 4 neat sandwiches and refrigerate.
Cut the vegetables into large chunks (1-11/2inches) and place in a roasting tray, add the garlic cloves and a few sprigs of thyme. Drizzle over the olive oil, season with salt and pepper, toss well and place in a pre-heated oven for 40-45 minutes.
Meanwhile, make some soft polenta by stirring 100g of ground polenta into 400ml of gently boiling salted water until a thick, porridge consistency is achieved. Keep stirring occasionally for 30 minutes or so over a very gentle heat. You may need to add some more liquid. When you are ready to eat, add a generous knob of butter and a handful of freshly grated parmesan and stir well. It should be soft and creamy in consistency and yellow in colour.
Frying the saltimbocca takes 50 seconds. Heat a little butter and olive oil in a frying pan. When almost smoking hot, put in the saltimbocca; 25 seconds on one side and then 25 seconds on the other.
Serve immediately with the polenta and the roasted vegetables.
