This elegant crostini, or opening nibble, is a play on both the classic Parisian sandwich of salty ham and sweet butter and the Italian summer tradition of pairing cured ham with melon. It very much reminds me of my family’s early years in Tuscany and the summer feasts at our neighbor's house where we were introduced to one of those strange Italian combinations that we couldn't get over: They always served melon (from their garden) with a really salty dry ham of their own. I love that combination but wanted to amp it up a little bit. So I mixed the cantaloupe with butter, making a delicious orange-colored spread with the consistency and texture of butter, but then the sweetness and flavor of melon.
Puree the melon cubes and butter in a food processor until completely amalgamated. This may take awhile, up to 10 minutes.
For each crostini, spread a generous knob of the cantaloupe butter on a piece of toast and drape half a piece of prosciutto on top.