Bring a large pot of water to a boil. Add the salt to the pasta water, then the pasta. Boil until al dente, for most pastas this is about 7 minutes.
While the pasta is boiling, bring a skillet to medium heat. Add the pumpkin, miso paste and red pepper flakes to the pan. Immediately begin to mix the ingredients together.
About 1/4 cup at a time, gradually add the milk to the pan, stirring constantly so that all of the ingredients meld together. During this time you are cooking the "raw" flavor out of the pumpkin, while simultaneously bringing out the umami flavor of the miso. Cook this mixture on the stove for about 4-5 minutes, stirring constantly.
When you see the sauce start to thicken and reduce, turn off the heat source but keep the pan on the stove.
When your pasta is done boiling, reserve 1/2 cup of starchy pasta water. Drain the rest.
Add the pasta directly into the pan with the sauce. Mix to combine, then using 1 tbsp at a time, gradually add in the pasta water. You might not need all of the water, so just add until you think the sauce is smooth, glossy, and coating the pasta.
Top with the breadcrumbs and serve warm!