½ teaspoon fennel seeds
½ teaspoon black peppercorns
2 (1-inch thick) slices day old bread, crusts removed and torn into 1-inch pieces (about 2 cups cubed, 2 ounces)
½ pound ground lamb (30% fat), medium grind if possible
⅓ cup dry bread crumbs, like panko
2 teaspoons minced garlic, plus 2 garlic cloves, smashed
¼ cup grated Pecorino Romano cheese
3 tablespoons finely chopped Italian parsley
½ teaspoon kosher salt
2 large eggs
¼ cup whole milk
3 tablespoons olive oil
1 tablespoon unsalted butter
1 (2-inch) sprig rosemary
¾ cup chicken stock
Preheat oven to 375°F. Toast the fennel seeds and peppercorns in a small skillet over medium-low heat until fragrant, about 2 minutes. Place ground lamb in a large bowl. Transfer spices to a spice grinder and pulverize. Note: If you do not have a coffee or spice grinder, you can use ground fennel powder, but the flavor will not have as much depth as the toasted, freshly ground spices. Add spices to ground lamb bowl. Add bread, in batches, to the spice grinder and pulse to create a fine crumb. Transfer crumbs to bowl.
Add the ground lamb, dry bread crumbs, minced garlic, pecorino cheese, 2 tablespoons of the parsley and salt. In a medium bowl, whisk the eggs until lightly beaten, then whisk in the milk. Pour the milk mixture into the meat mixture and mix until just combined. (Warm hands and touching the meat mix too much will melt the fat in the meat and make for a denser meatball. Wearing gloves is useful.) Chill mixture in the refrigerator for 20 minutes.
Place a little oil on your hands or gloves to prevent sticking as you form meatballs. Roll the meat mixture into about 16 (1-ounce) balls, each about 1 ½ inches in diameter. Chill until ready to cook.
Heat a large skillet over medium-high heat. Add the olive oil. Add the meatballs, making sure there is a little space between each. Sear until brown on one side, about 2 to 3 minutes. Flip and brown the other side, 1 to 2 minutes more. Push meatballs to the back half of the skillet. Add the butter, rosemary sprig and smashed garlic cloves to the front half, tilt the skillet slightly towards you and baste meatballs with the sauce for about 30 seconds.
Add the chicken stock. Roll the meatballs in the stock, transfer the skillet to the oven and cook for 5 minutes or until a cake tester inserted into the center of a meatball feels warm. Return the pan to the stovetop and let the stock simmer until it reduces to a glaze and coats the meatballs. Season the glaze with salt and pepper. Sprinkle with the remaining parsley just before serving. Note: If you are not serving the meatballs right away, brown them and then hold them colored but not fully cooked. Just before serving, glaze them, finish cooking and garnish with the parsley. This will keep them from overcooking.