Cook your crostini rounds as per recipe instructions through the link below if not done already. This can be done up to two days in advance and the crostini kept in an airtight bag or container. Make sure the crostini are completely cooled before storing otherwise the trapped heat moisture will re-soften them.
Preheat oven to 350F.
Cook off your ground beef if not done already. Combine the marinara sauce with the ground beef in a small bowl and set aside. Use as much or as little sauce as preferred.
In a second small bowl: Make your cheese mixture by combining the ricotta, Parmesan cheese, 1/4 cup mozzarella, dried basil, salt, and pepper.
Chill the cheese and beef mixtures separately until ready to serve.
When ready to serve, assemble the crostini by spooning approximately 1-2 Tablespoons of the cheese mixture on each crostini. Then add 1-2 Tablespoons of the beef mixture. Top off with the remaining mozzarella and a little Parmesan (if desired). Use as much cheese as desired. Repeat with all crostini pieces.
Bake the crostini at 350F until the top cheese is melted, approximately 5-7 minutes. Serve immediately.