Prepare and chill Pastry Dough. If using fresh pearl onions, place them in a saucepan of boiling water. Remove saucepan from heat and let stand for 5 minutes. Drain. When cool enough to handle, remove skins from onions; carefully halve onions. Set aside.
Preheat oven to 375 degrees F. Divide chilled Pastry Dough into 20 portions; shape each portion into a ball. Place one ball in each of twenty 2 1/2-inch muffin cups. Press dough into bottoms and up sides of muffin cups. Set aside.
In a medium bowl beat eggs with a fork until combined. Stir in milk, cheese, green onions, salt, and pepper. Ladle egg mixture into pastry crusts, filling each three-fourths full. On top of egg mixture in each muffin cup, arrange pairs of pearl onion halves and olive slices.
Bake in the preheated oven for 20 to 25 minutes or until a knife inserted near centers comes out clean. Let cool in muffin cups for 10 minutes. Using a sharp knife, carefully loosen sides. Carefully remove from muffin cups; serve warm.