1. Place a large Dutch oven over medium-low heat and add the bacon cubes along with 2 tablespoons of water. Cook, stirring often, until the fat is rendered and the bacon is browned but still chewy, about 6 to 12 minutes. Using a slotted spoon, transfer the bacon to a paper towel–lined plate, leaving the rendered fat in the pot.
2. Add the olive oil to the rendered bacon fat and bring the pot to medium heat. Place the sage leaves in the pan, spreading them out in a single layer, and cook for about 1 minute until they deepen in color but do not brown. Remove the sage leaves and drain them on a paper towel–lined plate.
3. To the sage-infused fat, add the onion along with a pinch of salt and the white pepper. Sauté for 4 to 5 minutes, or until the onion has softened. Stir in the garlic, thyme, coriander, and red pepper flakes, then add the cubed squash and the remaining salt. Continue cooking for about 5 minutes.
4. Stir in the cannellini beans and broth, then bring the mixture to a boil. Reduce the heat to a low simmer and cook for 20 minutes, stirring occasionally.
5. Remove 1 to 2 cups of the soup, including vegetables and beans, and transfer to a blender. Add the miso paste, blend until completely smooth, and then return the mixture to the pot. Remove the soup from the heat, stir well to combine, and adjust seasoning as needed.
6. Ladle the soup into bowls and top with the crispy bacon lardons, fried sage leaves, and a sprinkle of extra red pepper flakes if desired.