Heat the oil in a saucepan and sear the onions, bacon and meatloaf in it. Drain the beans and add them to the pot. Add the savory, stir everything well and simmer on medium heat with the lid closed for about 10 minutes.
In the meantime, prepare the roux. I always use 2 tablespoons of butter, 1 level tablespoon of flour and about 300 ml of stock, although this can be varied depending on taste and consistency. The preparation is as follows: Melt the butter in a small saucepan as soon as it is hot enough, sprinkle in the flour and stir well with a whisk, then add the stock and simmer on the lowest level for about 10 minutes the typical flour taste disappears. Stir in between and add stock as required to achieve the desired consistency and quantity. Add the roux to the beans and stir everything well. Stir in the crème fraîche. Season everything with savory, salt and pepper.