Place the cloves, cinnamon bark and lemon peel in a small linen bag or tea bag. Slowly heat the beer with the spice bag and let it absorb the aroma over low heat for a few minutes. Meanwhile, whisk the cream with the egg yolks and sugar. Now remove the spice bag, slowly add the beaten eggs and leave on the fire, stirring constantly, until the soup has the desired plumpness. Season with salt and pepper to taste. Meanwhile, toast the black bread cubes in hot butter. Now arrange the finished, creamy soup and serve with the still hot, crispy black bread croutons.