In Native American lore, the three sisters refer to corn, squash, and beans, which were traditionally grown together. The cobbler filling can be made ahead and baked with the topping just before serving.
To make Filling: Heat oil in 5-qt. Dutch oven over medium heat. Add onions, and cook 7 to 10 minutes, or until very brown. Add bell pepper, and cook 3 minutes more, or until bell pepper is softened. Sprinkle mixture with flour, and stir to coat. Cook 2 minutes, stirring constantly. Stir in 6 cups water, tomato paste, and garlic. Add black-eyed peas and herb bundle; cover pan, and bring to
a boil. Reduce heat to medium-low, and simmer 30 to 45 minutes, or until black-eyed peas are just tender.
Meanwhile, to make Topping: Warm milk in small saucepan until hot to touch. Remove from heat, and stir in sage. Cool 15 minutes.
Whisk together flour, cornmeal, baking powder, baking soda, and salt in medium bowl. Whisk together egg and cooled milk mixture in large bowl. Stir in cornmeal mixture.
Preheat oven to 425°F. Remove herb bundle from Filling. Stir in mustard, then add kale. Cover pan, and simmer 5 minutes, or until greens are wilted. Add butternut squash, stirring to combine, and season with salt and pepper, if desired. Cover, and simmer 10 minutes. Stir in chipotle pepper sauce.
Remove Filling from heat. Drop Topping over Filling with 2-Tbs. cookie scoop, or roll out on floured work surface, cut into rounds, and place rounds over Filling, covering completely. Bake uncovered 15 minutes, or until Topping is golden brown.