How to Make It
Preheat the oven to 350°. Line a large baking sheet with parchment paper.
In a large bowl, using an electric mixer, beat the butter at medium-high speed for 1 minute, or until light and fluffy. Add the eggs, 1 at a time, beating thoroughly between additions. Add the flour, Parmesan, prosciutto, pepper and salt and beat at medium speed until the dough just comes together. Do not overmix.
Scrape the dough out onto the prepared baking sheet. Using moistened hands, pat the dough into a 12-by-2 1/2-inch log. Bake the dough in the center of the oven for 25 minutes, or until the top is light golden. Remove from the oven and let cool for 10 minutes. Reduce the oven temperature to 275°.
Using a serrated knife, cut the log crosswise on the diagonal 1/2-inch-thick. Arrange the biscotti on the baking sheet cut side up. Bake for 20 minutes, or until the biscotti are golden and dry to the touch. Turn the biscotti over and bake for 15 minutes longer, or until golden and cooked through. Transfer the baking sheet to a wire rack and let the biscotti cool completely.