Preheat oven to 425 degrees.
Thoroughly wash and dry collards. In batches, stack collards then roll them lengthwise and cut them across the width into 1/2 inch ribbons.
Slice sausage on the bias into one-inch pieces and place in a 10×13 casserole dish along with tomatoes, oregano, and garlic. Drizzle with olive oil and bake for about 12 to 15 minutes or until sausage is cooked through.
Meanwhile, drizzle olive oil in a large, heavy-bottomed stock pot over medium-high heat. Add onions and sauté for about 5 minutes. Add half the collard greens, half the stock the pot and cook, stirring occasionally, until collards wilt a bit (making room for more). Add remaining collards and stock, and continue to cook until the collards are wilted and tender, about 15 minutes. Add beans, salt, and pepper, then cook uncovered until heated through (about 2 minutes).
Pour sausage, tomato, and garlic mixture into the collards mixture and gently stir to combine. Cook another 10 minutes over low heat. Adjust seasonings to taste.
To make the sage butter, melt butter in a small saucepan over medium heat, removing any foam from the butter with a spoon. Turn the heat up to medium-high and place the sage leaves in the butter for about 2 minutes or until crisp. Remove leaves and place on a paper towel.
Toast bread and rub garlic over the top. Ladle soup into bowls, top with toast and parmesan cheese, then drizzle with sage butter. Serve with a sage leaf and a few drops of Tabasco sauce (if desired).