In a small food processor, blend the jalapeño, cilantro, parsley, and 6 tablespoons of the olive oil until smooth and season with salt to taste. Set aside until ready to serve.
Heat 1 tablespoon of the remaining olive in a large 15-inch paella pan over medium-high. Add the yellow onion and bell pepper and saute for 8–10 minutes until soft. Add garlic and both paprikas and stir until fragrant, about 1 minute. Carefully add sherry, bring to a simmer, and cook, stirring constantly, until pan is almost dry, about 3 minutes.
Add the rice and toast until rice is coated and starting to turn translucent, about 3 minutes. Stir in 2 cups of the broth at a time while simmering and saffron and season with salt. Bring broth to a boil, adding the remaining broth until you've used it all and then reduce heat, and simmer until rice is cooked. If liquid evaporates and the rice is still al dente, add another cup of stock or broth or water and continue to cook. Nestle the clams into the rice and cover and continue to cook until clams open, 12–15 minutes. After 15 minutes, discard any clams that don’t open. Remove the pan from the heat, keeping it covered and let rice continue to steam for 10 minutes.
While paella cooks, heat a grill pan or skillet over medium-high. Separately, toss green onions and prawns with 1 tablespoon of oil each in their respective bowls; and season with salt and pepper. Char or grill the green onions, turning occasionally, until greens are charred and bulbs are tender, about 5 minutes. Char or grill prawns until cooked through and shells are charred, about 3 minutes per side. Finally, char or grill lemons until charred, about 1 minute per side.
Tuck the green onions and prawns into the paella. Drizzle dish with the herb infused oil and squeeze lemon juice on top. Place remaining lemons alongside the paella and serve.
Notes
A paella pot is an extremely wide skillet with low sides. It is also generally a thinner material to heat quickly. You can use whatever large skillet you have on hand.