In large saucepan, over medium-high heat, add pancetta and cook, stirring until crisp and brown, about 5 minutes. Remove from pan with slotted spoon and drain on paper towels. Discard all but 1/2 teaspoon fat from pan. Add onion to pan and stir often over high heat until very lightly browned, 4 to 5 minutes. Add potatoes, celery and broth. Cover, bring to a boil and cook until potatoes are tender, about 12 minutes. Add buttermilk and pancetta and stir until hot, 1 to 2 minutes. Season with salt and pepper. Remove from heat, stir in the Kerrygold Aged Cheddar Cheese, ladle into bowls and serve immediately.