Cut the raw potatoes into 2 cm cubes. In a wide cast iron casserole, heat equal amounts of butter and oil over medium-high heat. Fry the potatoes without a lid, stirring occasionally, for 15-20 minutes until they are golden brown. Do not salt at this stage.
Meanwhile, peel two small onions and cut into crescents. Add them to the potatoes and continue frying while stirring, without a lid, for 3-5 minutes. Then cover and cook over medium heat for another 2-3 minutes.
Clear a small area in the pot and add the roughly diced bacon sausage. Cook for 2-3 minutes on medium heat. Season the entire mixture with salt, marjoram, and caraway seeds if using. Stir well, cover, and cook over low heat for 10 minutes until cooked through.
If the gröstl is drying out, add a splash of water. Do not add broth. While the final cooking continues, fry the 2 eggs in a separate pan with butter or oil on medium heat until cooked to your preference.
Sprinkle the gröstl with fresh parsley and serve with the fried eggs and pickled cucumbers on the side.