1) Preheat the oven to 230C/Gas Mark 8.
2) Place the slices of prosciutto on a lightly greased baking tray. Bake until the prosciutto slices are almost completely crisp, about 6 to 8 minutes. The slices will crisp up even more as they cool. Reserve for garnish.
3) In a medium saucepan, bring the chicken stock to a boil. Reduce heat to a simmer. Blanch the asparagus in the chicken stock for 2 minutes. Remove the asparagus with a slotted spoon. Set the asparagus aside and keep the chicken stock at a low simmer.
4) In another medium saucepan, melt 15g of the butter. Add the shallot and cook until tender, about 3 minutes. Add the Arborio rice and stir to coat in the butter. Continue toasting the rice, stirring constantly, for about 3 minutes more. Add the Champagne and simmer until the liquid has almost evaporated, about 3 minutes. Add 120ml of the simmering stock and stir until almost completely absorbed, about 2 minutes. Continue cooking the rice, adding the stock 120ml at a time, stirring constantly and allowing each addition of stock to absorb before adding the next, until the rice is tender but still firm to the bite and the mixture is creamy, about 20 minutes total. Remove from the heat.
5) Gently stir in the asparagus, remaining butter, Parmesan, salt, and pepper. Spoon the risotto into serving dishes and garnish by breaking the crisp prosciutto into smaller pieces over the top of the risotto. Serve immediately.