If using fresh 2 lb whole octopus cleaned, fresh or thawed from frozen, freeze it for at least 24 hours beforehand and thaw overnight in the fridge — this breaks down the muscle fibers for a more tender result. Bring a large Pot of water to a rolling boil with the halved 0.5 whole yellow onion peeled, halved and 1 whole bay leaf. Using Tongs, dip the 2 lb whole octopus cleaned, fresh or thawed from frozen into the boiling water three times (the 'susto' or 'scare' technique), holding it submerged for 5 seconds each time, before fully submerging it. This helps the tentacles curl attractively.

Once fully submerged, reduce the heat to a gentle simmer. Cook the 2 lb whole octopus cleaned, fresh or thawed from frozen uncovered for 45–60 minutes, until a skewer or knife tip slides easily into the thickest part of a tentacle with no resistance. Skim any foam that rises in the first few minutes. Remove the 2 lb whole octopus cleaned, fresh or thawed from frozen with Tongs and let it rest on a Cutting Board for 10 minutes. Reserve the cooking liquid.

Peel and slice onions to about 1/8-inch thick — thin enough to cook quickly, thick enough to avoid scorching. Yellow or Spanish onions work best. Limit to 2 large onions per 12-inch Skillet to prevent steaming. Have your fat ready and keep a splash of water, broth, or wine nearby to deglaze if needed.

Heat a Skillet over medium to medium-high heat. Add butter, oil, or a mix and let it shimmer. Add sliced onions in large handfuls, stirring for 1–2 minutes per batch until they begin to soften — this prevents overcrowding. Once all onions are in, season with a pinch of salt. Cook over medium heat, stirring every few minutes, for 8–12 minutes total until soft, translucent, and lightly golden. To speed up softening, add 1/4 to ½ cup water or broth and cover; steam wilts the onions in a few minutes. Remove the lid once liquid evaporates and continue cooking uncovered. If the pan looks dry, deglaze with a splash of water, broth, or wine, scraping up any browned bits. Don't crank the heat — high heat burns the outside before the onions cook through.

Drizzle the 4 tbsp extra-virgin olive oil good quality, fruity Spanish variety preferred generously and evenly over the 2 lb whole octopus cleaned, fresh or thawed from frozen and 1 ½ lb waxy potatoes such as Yukon Gold, peeled and cut into ½-inch rounds. Dust with the 1 ½ tsp smoked paprika pimentón de la Vera; use sweet, hot, or a mix (and 1 ½ tsp smoked paprika pimentón de la Vera; use sweet, hot, or a mix if using), then finish with 1 tsp flaky sea salt Maldon or flor de sal and chopped 2 tbsp fresh flat-leaf parsley finely chopped, for garnish if desired. Serve immediately while warm — traditionally on a wooden board, straight to the table.