Place a large pot over medium-high heat; cook the bacon in the pot until crisp, 5 to 7 minutes. Stir in the onion and garlic; continue to cook until onions are translucent, about 5 minutes. Stir in the celery and carrot; cook another 2 minutes.
Pour the beef stock and beer into the pot; bring to a boil. Stir in the lentils, syrup, nutmeg, caraway seed, and celery salt; cover and cook for 45 minutes. Season with salt and pepper.