Bring a large pot of heavily salted water to a boil.
Cook the 1 box of wheat rotini pasta at a boil until tender yet firm to the bite, about 15 minutes.
Drain the pasta and transfer to a bowl.
In a saucepan, bring 2 cups of garlic mushroom marinara sauce to a simmer.
Add 1 cup of chopped kimchi, 1/2 cup of shredded cooked chicken, 1/2 cup of diced white onion, and 1 tablespoon of red chile paste to the saucepan.
Stir the mixture until completely mixed and heated through, about 5 minutes.
Mix 1 tablespoon of butter into the pasta and toss to coat.
Pour the marinara sauce mixture over the pasta.
Top the dish with 1 tablespoon of chopped scallions.