In a very large (12-inch) skillet, brown the chorizo over medium-high heat, about 8 minutes. Add one tablespoon of the oil. Add onion and sugar to the pan, and cook until the onion softens and begins to brown, about 7 to 8 minutes. Add the Worcestershire, beer, herbs and salt, usually ½ teaspoon, and simmer until most of the liquid has reduced and the flavors have blended. Taste and season with more salt if it needs it. Scrape the mixture into a small pan and keep warm over very low heat or in a low oven.
Pat the trout skin dry with paper towels and season with salt. Wipe out the skillet, add the remaining 1 to 2 tablespoons of the oil and set over medium high heat. When the oil is hot, carefully lay the trout fillets in the skillet, flesh side down in a single uncrowded layer. Cook until the trout is barely done, 3 to 4 minutes per side. Sprinkle with black pepper.
Remove the trout fillets to a plate and top with the warm chorizo and onion mixture. Garnish with more chopped herbs and serve immediately.