Preheat the oven to 350 degrees. Toast the bread lightly. Cut a hole in the center of each slice with a 1 1/2 inch circular cutter. Butter an ovenproof dish. Put the toast in it and break open an egg over each one so that the yolk falls in the hole in the center. Salt and pepper to taste. Spoon the buttermilk evenly over the four parts. Bake for 15 minutes.