Place oil in a deep pot, such as a tall 3-quart (2.8 L) pot, and heat over medium heat until shimmering. Add fennel seeds, mustard seeds, salt and red pepper flakes and heat for about 2 minutes or just until the seeds begin to pop. Add the beer, then squeeze the lemon wedges into the pot and add the lemons themselves to the pot as well. Give everything a good stir.

Add the shrimp and bring back to a boil. Use a large, sturdy spoon to get the shrimp on the bottom to the top and vice versa once during cooking. Cook just until shrimp are opaque, maybe about 3 to 4 minutes. Drain in a colander, discarding liquid.

Quickly pile the shrimp on a serving platter and set out on a newspaper-covered table. Add some hot sauce to the melted butter, offered in a dipping bowl alongside, and offer extra hot sauce for those so inclined. Peel and eat right away! Dive in!