Step 1

Melt the butter in a large pot over medium-high heat. Add the bacon and cook, stirring occasionally, until crisp, 4 to 6 minutes. Remove the bacon with a slotted spoon and transfer to a paper towel–lined plate.

Step 2

Reduce the heat to medium and add the onion, scallion whites and a big pinch of salt to the pot. Cook, stirring occasionally, until the onion is soft but not browned, about 8 minutes. Add the flour, celery seeds and white pepper; stir until combined.

Step 3

Add the potatoes, 3 1/2 cups water and 1 teaspoon salt to the pot. Bring to a boil over high heat, then reduce the heat to medium and simmer until the potatoes are tender but not falling apart, about 10 minutes.

Step 4

Remove the pot from the heat and transfer 1/2 cup of the potatoes to a blender. Add the half-and-half, cream cheese and parmesan and blend until very smooth. Gently stir the mixture into the pot along with the scallion greens, hot sauce and half of the bacon. Bring to a gentle simmer over medium heat; season with salt.

Step 5

Divide the soup among bowls. Top with cheddar cheese, the remaining bacon and chives.