In a large pot, bring generously salted water to a boil. Add the wide egg noodles and cook according to the package instructions until they are al dente. Once cooked, drain the noodles and set aside, optionally tossing with a little olive oil to prevent sticking.
In a large skillet, heat the olive oil and vegan butter over medium heat until shimmering. Add the finely chopped onion and sauté for about 3-4 minutes, stirring occasionally, until the onions are softened and translucent.
Incorporate the minced garlic into the skillet, cooking for an additional minute. Stir in the sliced mushrooms, cooking for 5-7 minutes or until they become tender and brown, releasing their flavorful moisture into the skillet.
Pour in the vegetable broth and soy sauce, then stir in the Dijon mustard and paprika. Allow the mixture to simmer for about 5 minutes, letting the flavors meld and the sauce reduce slightly for a richer consistency.
Lower the heat to a gentle simmer and add the sour cream (or cashew cream), mixing thoroughly to combine. Warm the sauce gently, taking care not to let it boil. Taste and adjust seasoning with salt and freshly ground black pepper as desired.
Carefully add the cooked noodles to the skillet with the mushroom sauce, tossing gently to ensure all the noodles are well coated in the creamy mixture. Allow to heat together for another 2-3 minutes, so the noodles absorb some of the sauce's flavor.
Plate the creamy stroganoff into bowls, garnishing each serving with a sprinkle of freshly chopped parsley for a vibrant touch and added flavor.
Notes
For a vegan alternative, substitute sour cream with cashew cream.