In a pot, boil 3 cups of lightly salted water. Add the charcoal powder and stir well. Add elbow pasta, stir, and cook until al dente. Drain the black water, coat the pasta with a drizzle of olive oil and set aside.
In a pot, melt butter and whisk in flour and charcoal powder. Cook until the mixture for about one minute. Then pour in cold milk while whisking, and cook for a few minutes until the sauce begins to thicken. Lower heat and add the cheese. Stir until fully melted. Season with salt. Combine the cooked pasta and sauce, and serve.