Clean squid by removing cartilage, separating tentacles, cutting off eyes, and cutting body into 1/4-inch rings. Rinse rings and tentacles well. Bring 1 gallon of water to a boil. Blanch squid for 30 seconds and drain. In a hot casserole saute onions in olive oil for 20 minutes without coloring.
Stab chorizo with a fork. Place chorizo links on baking sheet and place in 400 degree oven for 25 minutes. Let cool and cut into medium dice.
To casserole with onions add garlic and saute for five minutes. Add tomatoes and cook 10 minutes. Add squid and simmer for 30 minutes, letting natural juices release. Add wine and simmer until liquid is reduced. Add stock and simmer slowly until squid is tender. Add diced chorizo and heat through.
Prepare linguine according to package instructions. Drain and place in a bowl. Toss with olive oil, butter, and Parmesan. Garnish with chopped herbs.