Impress your company with this easy-to-prepare appetizer. Making your own ricotta is incredibly simple and doesn't require special equipment. Our microwave trick is foolproof. The pea mixture is quick and easy to make, but you can also mix it up ahead, along with toasting the bread, so that you can simply assemble the crostini when you are ready to serve your guests.
Combine milk, yogurt, and 2 teaspoons vinegar in a microwave-safe bowl, stirring with a whisk. Microwave at HIGH for 4 minutes. Gently stir to form small curds. Strain mixture through a sieve over a bowl; let stand 5 minutes. Reserve 2 tablespoons liquid. Discard remaining liquid. Combine reserved liquid, solids, and 1/8 teaspoon salt in a small bowl.
Combine remaining 4 teaspoons vinegar, remaining 1/4 teaspoon salt, peas, mint, 3 tablespoons oil, and 1/4 teaspoon pepper in the bowl of a food processor; pulse until spreadable but still slightly coarse.
Place about 1 tablespoon pea mixture on each toasted bread slice. Top each piece with about 1 teaspoon ricotta mixture. Sprinkle toasts evenly with remaining 1/4 teaspoon pepper, and drizzle with remaining 1 tablespoon oil.