In a large stock pot, heat olive oil on medium high. Add onion and garlic; sauté until onion softens, stirring often, approximately 5 minutes. Stir in mustard, sugar, vinegar and broth. Bring to boil.
Add greens, cover and cook 5 minutes, stirring often. Turn heat to low and simmer, covered, until greens are tender, approximately 1 to 1½ hours, stirring occasionally. Remove cover, return heat to medium high, add cranberries and cook for about 10 minutes, stirring often, allowing liquid to reduce and cranberries to plump.
Season with salt and pepper and garnish with nuts, as desired.