Named after a 75-millimeter gun used by the French in World War I, this is no cocktail to mess with. It will hurt you. Just kidding, it will make you feel really good. Especially when you take a sip from a glass rimmed with ground coppa sugar. Yeah, we did that. Just for you. Santé.
Preheat the oven to 400 degrees. Crisp the coppa on a baking sheet lined with foil or parchment, about 7 minutes. Alternatively, crisp the coppa in a small skillet over medium heat, about 6 minutes, turning the heat to low if the pan smokes too much. Use a metal lid a little smaller than the pan to keep the coppa flat. Remove to a paper towel-lined plate and let cool. Crumble into a spice grinder, add sugar and blitz until no more large bits remain. Dump onto a small plate.
Fill 2 (8-ounce) cocktail glasses with ice and water to chill.
Fill a cocktail shaker about halfway with ice. Pour in the gin, lemon juice and simple syrup to taste (some proseccos can be sweet, so taste accordingly) and shake to chill. Dump the ice water from the glasses and wet the outside of the rims with a little water or lemon juice. Press the glasses into the coppa sugar one at a time. Strain the cocktail, dividing between the glasses. Pour 4 ounces of prosecco in each glass and serve.