In a large pot filled with boiling water, cook the clams until they have opened, about 10-12 minutes. Discard any that do not open. Use a butter knife to shuck the clams from their shells. Set the clam meat in one bowl and the shells in another. Reserve about one tablespoon of the clam juice (water).
Using a large skillet over high heat, cook and crumble the chorizo until browned. Place the cooked chorizo along with the clam meat into a food processor. Wipe the skillet clean. Pulse the chorizo and clams in the food processor several times, until there's a consistent thickness with few whole clams and large lumps.
Place three tablespoons of butter into the cleaned skillet. Saute the onions until they are just beginning to caramelize then add the chopped peppers. Saute until softened.
Add the chorizo and clam mixture to the skillet. Stir well to combine then add the minced garlic, clam juice, lemon, and 2 tablespoons of Old Bay seasoning. Add 3 tablespoons of bread crumbs to the skillet, plus more as necessary if the mixture is still too wet. Season with salt and pepper, to taste.
Preheat the oven to 375 F. Break the clam shells at their hinges. Press a tablespoon of the clam mixture into each half shell. Arrange on a large baking sheet in a single layer.
In a small bowl, melt the remaining butter and whisk in the rest of the bread crumbs and Old Bay seasoning. Sprinkle the breading over the clams, as desired. Bake for 5-10 minutes, watching closely, until the breading is golden brown and crispy. Serve hot or cool to room temperature. Enjoy!