Prepare the Cabbage Ribbons:
Heat 1 tbsp butter in a large skillet over medium heat.
Add cabbage strips and sauté for 5-7 minutes, stirring occasionally, until softened but still slightly firm. Season with salt and pepper. Remove from heat and set aside.
Sear the Beef:
In the same skillet, heat olive oil over medium-high heat.
Add beef strips and sear for 1-2 minutes per side. Remove and set aside.
Sauté the Aromatics:
Lower heat to medium, melt 2 tbsp butter, and add onions. Cook until softened, about 3 minutes.
Stir in garlic and cook for another 30 seconds.
Cook the Mushrooms:
Add mushrooms and cook until they release their moisture and start to brown, about 5-7 minutes.
Make the Sauce:
Pour in the beef broth, Worcestershire sauce, mustard, paprika, salt, and pepper. Let it simmer and reduce for 5 minutes.
Thicken Naturally:
Stir in heavy cream and simmer for another 5 minutes until slightly thickened. (Let it reduce longer if you want it thicker.)
Finish with Sour Cream:
Lower heat to low, stir in sour cream and lemon juice. Return beef to the pan and simmer for 2 minutes, just to warm through.
Serve:
Spoon the stroganoff over the sautéed cabbage ribbons and garnish with fresh parsley.