• 3 tablespoons plus 2 teaspoons extra-virgin olive oil plus more for drizzling
• 6 small celery roots (celeriac; each about 4 ounces), unpeeled, trimmed with some stem still attached
• 1/2 cup (1 stick) unsalted butter, cut into 1" cubes
• 1 tablespoon coffee beans (optional)
• 1/4 cup oil-cured black olives, pitted, quartered lengthwise