Cook the elbow macaroni according to package directions, but reduce the "al dente" cooking time by 1 minute.
Chop the broccoli into smaller pieces if needed. Add the broccoli to the pasta for the final 4 minutes of the cook time.
Strain the pasta and broccoli and set aside.
Melt the butter over medium-low heat in the same saucepan used to cook the pasta. Sprinkle in the flour and allow to cook for about 3 minutes until slightly golden.
Add the nutritional yeast, miso paste, and spicy brown mustard. Whisk to combine with the roux.
Add the milk. Add only about ¼ cup at first, whisking to combine with the roux. This should create a thick paste. Continue adding the milk in ¼ cup increments, whisking each time.
Turn the heat up to medium-high. Whisk the sauce as it thickens. Continue until you can see the ribbon pattern remaining as you whisk.
Add the white wine vinegar and whisk to combine.
Return the pasta and broccoli to the pot. Stir to coat in the sauce.