Preheat oven to 350°.
Remove white papery skin from garlic head (do not peel or separate the cloves). Wrap head in foil. Bake at 350° for 45 minutes; cool 10 minutes. Separate cloves; squeeze to extract garlic pulp. Discard skins. Combine garlic pulp and 1/4 cup Great Northern beans; mash with a fork until pastelike. Stir in chopped sage; set aside.
Heat olive oil in a Dutch oven over medium heat. Add escarole to pan; cook 3 minutes or until escarole wilts, stirring frequently. Add remaining Great Northern beans, broth, and next 4 ingredients (through pink beans); bring to a simmer. Reduce heat, and simmer 20 minutes or until escarole is tender. Stir in garlic mixture; remove from heat. Cover and let stand 10 minutes before serving. Sprinkle with cheese. Garnish with sage sprigs, if desired.