Preheat oven to 425°F. Brush both sides of bread slices with 2 tablespoons of the olive oil. Place on baking sheet. Bake 5 to 7 minutes or until golden brown. Cool on wire rack.
Meanwhile, place peas, 1/4 cup of the pistachios, 2 tablespoons of the Parmesan, garlic powder, Italian seasoning, pepper, sea salt, lemon juice and remaining 1/4 cup olive oil in food processor; cover. Process until smooth, scraping down sides as necessary.
Spread about 1 tablespoon of the pea mixture onto each bread slice. Top each evenly with remaining 2 tablespoons each Parmesan and pistachios. Sprinkle with crumbled prosciutto, if desired.