First, whisk together the miso and butter until combined. Set aside.
Cut the corn kernels from the cobs and set the kernels aside.
Add the cobs to a large pot of water and bring to boil. Although I typically salt my pasta water, I tend not to here because miso brands sometimes differ in how salty they are and it’s always easier to add a bit of salt at the end than take it away. Cook the pasta according to the instructions.
While the pasta is cooking, heat vegetable oil in a large skillet over medium-high heat. Add most of the scallions, reserving a handful or so for garnish, and let cook briefly, about 20-30 seconds. Add the corn kernels and the miso-butter mixture and cook, stirring, until the mixture begins to brown and caramelize slightly. If the pasta is not yet done, remove the corn-miso mixture from the heat until the pasta is cooked.
When the pasta is done, drain, reserving a ½ cup or so of the pasta water, and add the pasta to the skillet with the corn-miso mixture. Return to low heat and toss the pasta until it’s glossy and coated in the miso-butter. Add the mascarpone and toss again until coated. Loosen with pasta water as needed and season with salt and pepper to taste. Garnish with remaining scallions and enjoy hot.
