Add the lentils to a stock pot and cover with a few inches of water. Add the 2 whole cloves of garlic and bay leaf and bring to a boil. Reduce the heat and simmer until tender but still toothsome, about 20 minutes. Drain and discard the garlic and bay leaf. Set aside the lentils for later.
Add 3 tablespoons of olive oil to a large nonstick skillet, warm over medium heat, and add the carrot, celery, and onion. Season with fresh cracked salt and pepper. Sauté, stirring occasionally, for about 10 minutes, until well cooked and the onions are starting to turn golden.
Add the minced garlic and thyme to the pan and sauté for a minute or two more, until fragrant. Add the lentils to the pan, plus 1/2 cup beef broth. Stir and cook for a minute or two until warmed. Turn off the heat, stir in the parsley, mustard, and white wine vinegar. Season liberally with salt and pepper, and set aside.
In another large skillet, place the bratwurst. Add the two beers and as much water as necessary to almost cover the sausages. Turn the heat to high, bring to a boil, then reduce the heat and simmer for 10 or 15 minutes, flipping halfway through, until cooked through. Remove the sausages from the pan and set aside. Discard the beer.
Turn on the broiler, place the sausages on the broiler rack and put a pan underneath if needed to catch the juices. Broil the sausages on high for 5 to 8 minutes on each side until nicely charred (exact timing depends on the strength of your broiler and how done you like your sausages). Remove from the broiler and let rest for a few minutes before slicing into rounds.
Add a few scoops of lentils onto each serving plate, drizzle with olive oil and sprinkle with flaky sea salt. Top with sliced sausage and enjoy!