Ingredients

• 1 pound zucchini, sliced into 1/4-inch-thick rounds
• 3 sprigs fresh oregano
• 2 cups apple cider vinegar
• 1/3 cup sugar
• 2 teaspoons black peppercorns
• 1 teaspoon kosher salt
• 1 teaspoon fennel seed
• 1/2 teaspoon red pepper flakes
• 1 bay leaf
• 1 cup coarsely grated Parmesan
• 1 tablespoon all-purpose flour
• 1/4 teaspoon freshly ground black pepper
• 1 garlic bulb
• 1 teaspoon olive oil
• 1 teaspoon kosher salt
• 1 cup mayo
• 6 cloves roasted garlic (see Cook's Note)
• 2 tablespoons lemon juice
• 2 teaspoons freshly chopped parsley
• 1 teaspoon freshly chopped oregano
• 1/2 teaspoon kosher salt
• 1/4 teaspoon freshly ground black pepper
• 1 1/2 pounds lean ground beef
• 1/2 pound ground lamb
• 1 tablespoon kosher salt
• 1 teaspoon freshly ground black pepper
• 3 tablespoons olive oil
• 6 ciabatta rolls, halved
• Extra-virgin olive oil, for drizzling
• Roasted Garlic Mayo
• 6 Burger Patties
• 4 medium tomatoes, sliced into 1/4-inch rounds to yield 12 slices
• 12 Zucchini Pickle slices
• 6 Parmesan Frico rounds

Instructions

1. For the pickles: Place the zucchini slices and oregano in a large jar or heat-safe container. Heat the apple cider vinegar, sugar, peppercorns, salt, fennel seed, red pepper flakes and bay leaf in a medium saucepan, stirring until the sugar and salt have dissolved, about 2 minutes. Pour the pickling liquid and spices into the jar. Let cool completely, uncovered. Place in the refrigerator for at least 24 hours and store for up to 6 weeks.
2. For the frico: Place an oven rack in the center of the oven and preheat the oven to 375 degrees F. Line a baking sheet with parchment paper or a silicone mat. Toss the Parmesan, flour and pepper together in a large bowl, making sure the flour is evenly distributed throughout the cheese. Arrange mounds of 2 tablespoons of cheese 4 inches apart on the baking sheet and flatten each mound slightly with a spatula to form a 3-inch round. Bake the frico in the oven until golden brown, about 10 minutes, rotating the sheet halfway through baking. Cool the frico on the baking sheet for 2 minutes, and then gently transfer to a wire rack to cool completely.
3. For the mayo: In a small bowl, stir together the mayo, garlic, lemon juice, parsley, oregano, salt and pepper.
4. For the patties: In a large bowl, combine the beef, lamb, salt and pepper. Form the mixture into six 4-inch-diameter patties, each about 1/2-inch thick. Drizzle the patties with olive oil. Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Grill the patties until they are grill marked and cooked through, about 4 to 5 minutes per side. Allow the patties to rest for 5 minutes.
5. For the burgers: Drizzle the cut side of the ciabatta rolls with olive oil and grill lightly until toasted, about 1 to 2 minutes. Spread the garlic mayo over the bottom halves of the grilled bread. Place the burger patties on the bread and top each patty with 2 tomato slices, 4 pickle slices and 1 frico round.