Heat the butter in a large cast iron skillet over medium heat until sizzling hot. Add the onion, garlic, 1 tablespoon parsley, and bay leaves and cook and stir until the garlic is aromatic, about 1 minute. Squeeze the juice from the lemons into the skillet, reserving 2 of the squeezed halves. Add the beer, worcestershire, hot sauce, and red pepper flakes and stir to mix. Thinly slice the reserved lemon halves and add to the skillet. Bring the mixture to a low boil and simmer for 3 to 4 minutes.
Season the shrimp all over with salt and pepper and add to the skillet. Cook, stirring occasionally, until the shrimp are pink and cooked through, about 4 or 5 minutes. Remove and discard the bay leaves. Season with salt and pepper if needed and sprinkle with the remaining 2 tablespoons parsley.