Preheat oven to 375°F.
Pour oil into a heavy bottom skillet, over medium-low heat.
Add all soffrito ingredients into skillet, except tomatoes, and stir. Season with salt and pepper.
Allow mixture to caramelize for about 1 hour, stirring occasionally.
Stir in tomatoes and cook down an additional 20 minutes or until the mixture becomes thick. Season with salt and pepper.
Remove from heat an allow to cool completely.
Pour stock and saffron into a medium saucepan, place over medium heat and bring to a simmer.
Poach seafood in the saffron infused stock, one type at a time, until shrimp has just cooked through and the clams and mussels have just opened. Remove from stock and set aside covered.
Pour oil into a 14-16” paella pan (or heavy bottom skillet) and place over medium-high heat.
Season chicken piece with salt and pepper and sear on each side for about 3 minutes. Remove from heat and set aside.
Brown chorizo for about 1 to 2 minutes and remove from pan. Set aside.
Drain all but 2 tablespoons grease from pan and add rice, chorizo and 1 cup soffrito to pan and season with salt and pepper. Stir together and sauté for about 2 minutes.
Pour hot stock over rice mixture and bring to a boil. Once mixture has come to a boil add chicken pieces back into the pan (gently tucking each piece down into the rice mixture). Place paella pan into the oven, covered with foil, and baked for about 10 to 15 minutes. Remove cover and continue to bake for an additional 10 to 15 minutes or until all the liquid has evaporated and the rice has cooked through.
Remove from oven and top with poached seafood (slightly warm seafood, if needed).
Finish with a sprinkle of parsley, lemon wedges and sweet peas, if using. Serve.