Creamy mozzarella meets piquant green olives and rich artichoke hearts in this gorgeous vegetarian antipasto. Serve with bread—and maybe with glasses of aperitivi on the patio, you'll feel like you're in Italy.
Fit a large pot with a steamer rack; add water until it reaches just below rack. Place artichokes in steamer, stem-sides up. (If necessary to fit, trim top third from each with a serrated knife.) Cover and bring to a boil, then reduce heat to medium and steam, adding more water as needed, until the tip of a knife slides in and out of stems easily, 30 to 35 minutes. Remove artichokes; when cool enough to handle, remove leaves and reserve for another use. Scoop out and discard chokes. Cut hearts into halves or quarters.
Combine oil, peppercorns, thyme sprigs, lemon zest, garlic, and 1 teaspoon kosher salt in a small saucepan over medium-high heat. Cook until bubbles form around edges; remove from heat. Stir in lemon juice, then artichoke hearts; let stand, tossing occasionally, until cool, about 30 minutes. Stir in olives. (Dish can be made to this point and refrigerated in an airtight container up to 3 days; bring to room temperature before serving.)
Preheat oven to 450 degrees. Brush cut sides of bread with oil; season with kosher salt and pepper. Place on a baking sheet; toast until golden brown on edges, about 8 minutes.
Arrange artichoke mixture on a platter with cheese. Garnish with thyme sprigs and flowers, sprinkle with Hawaiian or kosher salt, drizzle generously with oil, and serve with toast.