Heat lard over medium heat until just before smoking. Add the carrots and onions until the onions are translucent. Toss the leeks in and sautee all for another minute.
2 tablespoons lard, 2 medium onions, 2 stalks leek, 2 medium carrots
Pour in the stock and beer and add the bay leaf and seasonings. Bring to a boil, turn the heat to medium low, and cover. Simmer for an hour.
2 stalks leek, 2 cups pork stock, 2 cups dark beer, 3 cloves, 1 bay leaf, 2 teaspoons brown mustard
Add in the rye bread, give it a good stir, and simmer another hour with the lid off.
8 slices cocktail rye bread
Use an immersion blender or put in a blender and puree.
If the sauce is too thin, bring the pot back to a boil, make a slurry of 2 tablespoons of arrowroot powder and a little water. Gradually add the slurry while stirring until thickness is just where you want it.