Bring a large pot of salted water to a boil. Cook the pasta until al dente. Save a few tablespoons of the pasta water, and then drain the pasta in a colander.
While the pasta is cooking, in a large skillet set over medium heat, add the chopped bacon. Cook until the bacon is crisp. Remove the bacon with a slotted spoon, leaving as much of the fat behind as possible.
With the heat still on medium, add the kimchi and garlic. Cook until fragrant, about one minute. Add the red pepper paste, and stir until it is combined.
Add the cooked pasta to the skillet along with the butter and the reserved pasta water. Stir continuously until the pasta is coated with the sauce. Season to taste with salt.
Serve the pasta garnished with scallions, sesame seeds, and the cooked bacon. Add more salt if needed.