Vegetable oil cooking spray
2 packed cups fresh basil leaves
1/3 cup toasted pine nuts, see Cook's Note
2 tablespoons fresh lemon juice
1 clove garlic, peeled and smashed
Zest of 1 large lemon
1/2 teaspoon kosher salt, plus extra for seasoning
1/4 teaspoon freshly ground black pepper, plus extra for seasoning
1/3 cup extra-virgin olive oil
1/3 cup (1 1/2 ounces) grated Parmesan
3 medium zucchini, trimmed and each cut into ten 1/2-inch-thick rounds
Six 1/8-inch-thick slices prosciutto, quartered
2 tablespoons extra-virgin olive oil
Special equipment: Six 6-to-8-inch bamboo skewers soaked in water for 30 minutes to prevent scorching, or 6 metal skewers.
Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Spray the grill with vegetable oil cooking spray.
For the pesto: Pulse the basil, nuts, lemon juice, garlic, lemon zest, salt and pepper until finely chopped in a blender or food processor. With the machine running, gradually add the oil until the mixture is smooth and thick. Add the cheese and pulse until just incorporated. Season with salt and pepper.
For the skewers: Thread 1 round of zucchini onto a skewer. Thread 1 crumpled piece of prosciutto onto the skewer. Repeat 3 more times ending with a round of zucchini. Each skewer should have 5 rounds of zucchini and 4 pieces of prosciutto. Drizzle the skewers with olive oil and grill, turning occasionally, until the zucchini are tender, about 5 minutes.
Brush the skewers with the pesto, using a pastry brush, and serve.
To toast the pine nuts, arrange in a single layer on a baking sheet. Bake in a preheated 350 degrees F oven until lightly toasted, 5 to 6 minutes. Cool completely before using.