Sautee the holy trinity and serrano pepper in oil until they sweat. You may want to season the veggies at this point, but beware -- unless you are familiar with the salt content of the hocks, tread lightly.
Add drained peas and remaining ingredients, except toasted flour, and bring to a boil. Then, cover, and simmer for two hours, or until peas are tender.
When peas are tender, remove and debone the hocks, chop the meat into bite-sized chunks, and return to pot. Continue to simmer.
In a sautee pan, toast the flour over medium heat until a medium to dark carmel color -- ten minutes should do the trick. Add it to the peas a bit at a time, and stir after each addition, until desired thickness is achieved.