Poussins, which are young chickens, can be purchased from most butchers, but you may need to order them in advance. You can substitute Cornish game hens.
For the Poussins: Toast coriander seeds in a dry skillet over medium-high heat for 2 minutes, shaking skillet occasionally. Crush coriander seeds, and combine with peppercorns and cilantro.
Whisk together oil, citrus zests and juices, bay leaves, salt, and 2 teaspoons coriander mixture in a nonreactive bowl. Rub over poussins. Cover, and refrigerate overnight. (Reserve remaining coriander mixture, refrigerated, for another use.)
Make the Vegetables: Place a steamer basket in a large pot filled with 2 inches water. Bring to a boil. Add artichokes and bay leaves; cover, and steam until just tender, about 20 minutes.
Meanwhile, heat butter in a skillet over medium-high heat. Add leeks and fennel, and cook until just softened, about 8 minutes. Reduce heat to medium-low. Cover, and cook until completely tender but not caramelized, about 30 minutes.
Preheat grill to medium-high. (If you are using a charcoal grill, coals are ready when you can hold your hand 5 inches above grill for just 3 to 4 seconds.) Remove poussins from marinade, and pat dry. Season with salt and pepper. Grill poussins, flipping once, until skin is golden brown and a meat thermometer inserted into the thickest part (avoiding the bone) registers 165 degrees, about 12 minutes per side. Grill the artichokes until warmed through, about 5 minutes. Grill the lemon halves, cut sides down, until marked, about 5 minutes.
Arrange poussins and artichokes on top of leeks and fennel. Garnish with fennel fronds, lemons, and bay leaves.
