Cut the chorizo in half lengthwise and then crosswise into about 1/2-inch pieces. Heat up the olive oil in a big saucepan, over med-high heat. Add the chorizo and cook for approximately 5 minutes or until the pieces are lightly browned . Remove the chorizo and set aside.
Remove all but about 2 T of the chorizo flavored oil from the pan. measure the chorizo-flavored oil from the saucepan and put the pan back over medium-low heat. Add the onion and cook for about 4-5 minutes. Add the bell peppers and cook for another 2 minutes. Add the garlic and cook about 1 more minute. Next, add the sherry and simmer for about 2-3 minutes, or until it has reduced by approximately half.
Next, add the beans, tomatoes and chicken stock to the saucepan. Simmer this for about 15 mintues. Mash the mixture a bit to crush some of the beans. Lastly, stir in the chorizo and season with salt and pepper , to taste.