In a stockpot or Dutch oven over medium heat, melt the butter. Add the bacon and cook until crispy and most of the fat is rendered, about 8 minutes. Set the bacon aside for later use, leaving the fat in the pot.
In the same pot over medium heat, saute the sweet potato, shallots, garlic and bell pepper, stirring frequently, until the shallots are tender and translucent, about 3 minutes. Add the thyme, sage and bay leaf. Season with salt and pepper. Add the flour and curry to the vegetables and stir until incorporated. Cook for another 2 minutes.
Add the corn, chicken stock, heavy cream and sherry vinegar. Bring to a simmer and cook, covered, until the sweet potato is tender, another 20 to 25 minutes. Season with salt and pepper.
Plate into individual bowls and garnish with the crispy bacon and chives.