Using a round cookie cutter, cut a hole out of the center of each piece of bread. Brush the top of each slice of bread with ½ teaspoon olive oil. Press some chopped walnuts onto the top surface of each piece of bread, pressing them in so that they adhere. Heat 2 teaspoons oil in a large cast iron skillet
over medium heat. Add two pieces of bread, walnut side down. Cook a few minutes until toasted and then flip the bread over (don’t worry if some of the walnuts fall off- they will get nicely toasted in the skillet). Carefully crack an egg into each hole. Cover the pan with a lid and cook for a few minutes until whites are set and yolks are cooked to desired firmness. Remove from skillet. Add the remaining 2 teaspoons oil to the skillet and cook the remaining toads in a hole. If desired, toast the bread circles in the pan and serve.