Rinse 1 ⅓ pounds pork kidneys under cold water, then soak in 2 cups milk for 2–3 hours (or overnight in the fridge) to reduce their strong aroma. Rinse again and drain.
Remove any visible membranes. Then cut the kidneys in half lengthways, and trim out the white ureters and fat from the middle, keeping only the clean flesh.
Slice the kidneys into thin strips (¼ inch / 0.6 cm) or small cubes (⅓-⅔ inch / 1-1.5 cm). Rinse in cold water again and drain.
Peel and finely chop1 medium onion. Cut 3 ½ ounces bacon into small cubes.
Melt 1 Tablespoon pork lard in a saucepan over medium heat. Add chopped onions and cook until slightly golden. Stir in 1 teaspoon caraway seeds and bacon, cooking for another minute.
Increase to medium-high heat, add drained kidneys, and fry them for 2-3 minutes while stirring constantly. Do not add salt yet, as it may toughen the kidneys.
Once seared, add a little hot broth or water. Reduce heat to low, cover, and simmer for 30 minutes, stirring occasionally. If the liquid evaporates and the kidneys stick, add a bit more hot broth—just enough to prevent burning.
When the kidneys are nearly tender, increase the heat and reduce the liquid until almost gone. Sprinkle with 1 Tablespoon all-purpose flour, stir well, and fry for 30 seconds.
Remove from the heat source. Gradually add app. 1 ½ cups lukewarm broth to the saucepan, stirring to create a smooth, slightly thin gravy. Lower the heat and put it back on the stove. Cover with a lid, and simmer for 15 minutes, stirring occasionally.
Finally, season with salt to taste and enjoy your rich, flavorful kidney stew!