Place the noodles in a bowl and cover with hot water. Allow them to sit for 5 minutes until they soften and the strands separate.

Mix the sauce by combining the gochujang, soy sauce or tamari and mirin. Whisk until smooth. Set aside.

Cut the white parts of the scallions into 2-3cm pieces (about 1 inch) and finely slice the green parts. Keep them separated and set them aside.

Place a medium fry pan (skillet) on medium high heat. Add 1-2 tbsp oil and swirl it around the pan so it is evenly coated. Add the mushrooms and toss for about 2-3 minutes until softened. Season with sea salt and black pepper.

Add the white parts of the scallions and fry for 1 minute until the scallions are softened and everything is starting to caramelize. Reduce heat to medium and add the noodles and the sauce, along with 1/4 cup water (this helps to loosen everything up and deglaze the pan). Toss to coat the noodles. Throw in the butter, and mix until the butter is melted. Taste and if needed, season with a little salt and black pepper.

Toss in 3/4 of the scallions, keeping the rest for topping, and toss to combine.

To serve, top with remaining scallions.