Soak bread in milk for 10 minutes. While that occurs, melt butter in a large skillet set over medium to medium-high heat. Add onions and cook 5 minutes. Add the beef and cook until crumbly and cooked through. Remove from the heat; drain excess fat.
Preheat the oven to 350 degrees F. Squeeze the milk out of the bread; reserve the milk. In a small bowl. Thoroughly mash bread in a small bowl with a fork. Thoroughly mix bread into meat mixture. Mix in remaining ingredients, except reserved milk, eggs and bay leaves.
Pack the meat mixture into a lightly buttered 9-inch x 13-inch casserole. Cover and bake 20 minutes. Beat eggs with the reserved milk. After 20 minutes of baking, uncover bobotie and pour on the egg mixture. Garnish top with bay leaves. Bake, uncovered, 25 to 30 minutes more, or until top is light golden and set.