The butternut squash-goat cheese spread can be made up to three days in advance and should be stored in an airtight container in the refrigerator. Let it come down to room temperature before assembling the crostini so it spreads more evenly. The crostini can be made up to a day in advance and stored in a resealable plastic bag or airtight container at room temperature. I recommend making the crispy prosciutto and sage right before assembling the crostini.