Preheat oven to 400 degrees. Place 2 whole acorn squash (about 2 pounds each) on a rimmed baking sheet; bake, turning occasionally, until very tender when pierced with the tip of a paring knife, about 1 hour.
When cool enough to handle, halve each squash lengthwise. Scoop out and discard seeds; scrape out flesh from squash halves, and transfer to a food processor (discard skin). Process until smooth.
4 strips bacon, cut crosswise into 1/2-inch pieces
1 medium onion, finely chopped
1/2 pound kale, thick stems removed, leaves finely chopped (about 8 cups)
4 cups , or 2 packages (12 ounces each) frozen winter squash puree, thawed Acorn Squash Puree
Coarse salt and ground pepper
Cook bacon in a large saucepan over medium heat, stirring occasionally, until crisp, 4 to 5 minutes. Using a slotted spoon, transfer bacon to a paper-towel-lined plate; set aside.
Add onion to fat in pan, and cook until softened, 4 to 5 minutes. Add kale; cook until soft, 3 to 4 minutes.
Add squash puree and 3 cups water (or more if necessary to achieve desired consistency); bring just to a boil. Season generously with salt and pepper. Serve, garnished with crumbled, reserved bacon.