Fill the top and bottom of your Römertopf with water and let it sit for 30 minutes.
Heat olive oil and butter in a large pan over medium heat.
Brown the bacon cubes until they are crispy. Remove them with a slotted spoon and place them on a plate with paper towels.
Add the onions and carrots to the pan and cook for 2-3 minutes. Remove them from the pan and place them in a bowl or deep plate.
Drain the Römertopf of water.
Brown the beef cubes on all sides - cook in batches so the pan doesn't cool down! Then place the cubes in the Römertopf.
Cook the mushrooms for 3-4 minutes until they are lightly browned.
Add garlic and tomato paste and cook for another 1-2 minutes.
Pour the onions, carrots, and mushrooms over the meat in the Römertopf.
Add salt, pepper, and bouquet garni.
Pour red wine over the ingredients in the Römertopf. Ensure that it covers the ingredients. If necessary, you can add more red wine or a bit of stock.
Put the lid on the Römertopf and place it in a cold oven.
Set the oven to 160°C and let the dish simmer for about 3 hours or until the beef is tender!
Meanwhile, prepare the pearl onions.
Heat a pan over medium heat and add butter.
When it has foamed, add the pearl onions and toss them in the butter.
Add sugar and a pinch of salt and toss.
The onions are ready when the sugar is caramelized and coats the onions. If it’s too thick and sticky, add a bit of water or wine.
Remove the lid from your Römertopf, discard your bouquet garni, and season to taste with salt and pepper.
Top with the pearl onions and chopped parsley and serve with mashed potatoes.