Add the whole can of beans (liquid & all) & the cooked sausage to the pot. Bring mixture to a boil over medium-high heat & cook 1 minute. Reduce heat to low & simmer 10 minutes more.
Heat broiler. Mound 2 teaspoons parmesan cheese on each bread slice & place on baking sheet. Broil until cheese & bread are lightly toasted, about 1 to 2 minutes. Serve toasts with soup.