Melt butter in heavy saucepan over medium heat. Add sausage. Cook until no longer pink, breaking up with spoon, about 5 minutes. Add sliced ramp bulbs and stems. Saute until almost tender, about 2 minutes. Add rice and stir 1 minute. Add vermouth. Simmer until liquid is absorbed, about 1 minute. Add 3 cups chicken broth, 1 cups at a time, simmering until almost absorbed before next addition and stirring often. Continue cooking until rice is just tender and risotto is creamy, adding more broth if dry and stirring often, about 18 minutes. Mix in green tops and 1/2 cup grated Parmesan cheese. Season risotto to taste with salt and pepper. Serve, passing additional grated cheese separately.