Set a large pot of water to boil over medium-high heat on the stovetop.
Make the sauce by whisking together the peanut butter, poppy seed butter, soy sauce, fish sauce, sesame oil, maple syrup, and minced garlic. Set the Halloween sauce aside.
Cut a total of 12-16 ¼-inch (0.6 cm) thick carrot coins off the thick ends of the carrots. Slice two small notches from each carrot coin to make the carrot pumpkins. (Watch the video below!) Set these “pumpkins” aside. The notches that were cut away can be saved for another recipe.
Using a vegetable spiralizer, spiralize the long, unused pieces of carrot into carrot noodles. Thinly slice the pieces that don’t fit in the spiralizer by hand. Put the carrot spirals aside.
When the water in the pot starts to boil, add the black soybean spaghetti and turn the heat down to medium. Cook the pasta for three minutes, then add the raw shrimp to the pot and continue cooking for 2-3 minutes.
Note: if you use another type of pasta, adjust the cooking time according to the directions on the box. Add the shrimp during the last 2-3 minutes of cooking time.
Drain the shrimp and spaghetti in a colander. Return it to the pot (off the heat), and stir in the carrot spirals and the sauce.
Divide the Halloween spaghetti between the serving bowls. Garnish with the pumpkin-shaped carrots, sliced scallions, and pumpkin seeds. Happy Halloween!