Preheat a large skillet over medium-high heat. Add 1 Tbsp (15 mL) butter and swirl to coat the bottom. Add onion and cook, stirring occasionally, until softened, about 5 minutes.
Add remaining 1 Tbsp (15 mL) butter, mushrooms and lentils to the skillet and stir to combine. Season with salt and pepper to taste and stir again. Cook for 5-6 minutes, stirring occasionally, until mushrooms have cooked down.
Meanwhile, whisk together broth, Dijon, smoked paprika, and garlic powder in a small bowl. Season with salt and pepper, if desired. Set aside.
When the mushrooms have cooked down, sprinkle flour over top, then stir to coat. Stir in spiced broth mixture to the skillet and bring to a simmer. Continue to cook, stirring often, until the sauce has thickened, about 8-10 minutes.
Remove skillet from heat and stir in yogurt and Worcestershire sauce. Sprinkle with fresh parsley.
Serve stroganoff over noodles, mashed potatoes, or rice, if desired. Enjoy!