Yield: 4 servings
1 cup fresh sage leaves
2/3 cup walnut halves, toasted
½ cup grated Parmesan cheese
½ teaspoon lemon zest
½ teaspoon salt
1/8 teaspoon ground black pepper
1 small clove garlic
½ to 2/3 cup extra-virgin olive oil
8 slices sourdough bread
8 thin slices prosciutto
8 thin slices tomato, patted dry
16 thin slices whole milk mozzarella cheese
2 tablespoons vegetable oil
1. In the work bowl of a food processor, combine sage, walnuts, Parmesan, lemon zest, salt, pepper, and garlic. Pulse until minced, 6 to 8 times. With food processor running, slowly add ½ cup olive oil until mixture is smooth. Add remaining 2 tablespoons olive oil, if needed. Scrape into a small bowl or jar. Spread 1 tablespoon sage pesto over 1 side of each bread slice.
2. Divide prosciutto, tomato, and mozzarella among 4 bread slices. Cover with remaining 4 bread slices, pesto side down.
3. Brush the flat side of a cast-iron griddle with vegetable oil; heat over medium heat. Place panini on griddle; brush tops with oil. Press panini with a spatula or another cast-iron pan to flatten. Cook, pressing occasionally, until bread is golden brown and cheese melts, approximately 3 minutes. Turn panini over; flatten with spatula. Cook until golden brown.