How to Make It
Heat oven to 375° F. Place the baguette slices on a baking sheet and brush with 2 tablespoons of the oil. Toast until golden, 10 to 12 minutes.
Meanwhile, in a food processor fitted with the metal blade, puree the peas, ricotta, scallion, and Parmesan with the remaining 2 tablespoons of oil, ½ teaspoon salt, and ¼ teaspoon pepper, scraping down the sides of the bowl occasionally, until the Parmesan is broken down and the mixture is nearly smooth.
Spread the pea mixture on the crostini and top with grated Parmesan, if desired.