First, make the butternut squash-goat cheese spread. Preheat the oven to 400 degrees Fahrenheit. Line a large jelly roll pan with aluminum foil. In a medium bowl, combine squash, 1 tablespoon olive oil, ¼ teaspoon salt, pepper, nutmeg and cayenne. Pour onto prepared jelly roll pan and roast in oven for 20 minutes, or until squash is fork tender.
Place roasted squash in a food processor with goat cheese, garlic, rosemary, and additional ¼ teaspoon salt. Once mixture has begun to break down, slowly stream in additional 2 tablespoons of olive oil and pulse until mixture is nice and creamy with minimal lumps.
Next, make the crostini. When you remove the squash from the oven, turn the broiler on high. Place baguette slices on a large cookie sheet and brush both sides of the bread with olive oil. Place under broiler for about 1 ½ minutes per side, or until both sides are a nice golden color. Keep a close eye on these, as they can go from golden to burnt very quickly.
Finally, make the crispy prosciutto and sage. Place 2 tablespoons olive oil in a large saute pan over medium-high heat. Once olive oil is heated, add prosciutto. Depending on the size of the pan, you may need to do this in batches. Cook the prosciutto in the oil until crispy, about three minutes per side. Remove prosciutto from pan and place on a plate covered with a paper towel to absorb some of the oil.
Add 2 more tablespoons of olive oil to the saute pan (still over medium-high heat) and then add sage leaves. Cook until crispy and fragrant, two to three minutes. Remove the sage leaves to the same plate that the prosciutto is on to drain excess oil.
Transfer prosciutto and sage to a cutting board and chop up roughly.
Now we’re ready to assemble the crostini. Spread a generous amount (about a tablespoon) of the butternut squash-goat cheese mixture over each piece of crostini, then top each piece with prosciutto and sage. Enjoy immediately.