Vegetarian Stroganoff Recipe for a Creamy Dinner

Name: Vegetarian Stroganoff Recipe for a Creamy Dinner
Prep time: 15 min
Cook time: 25 min
Total time: 40 min
Cuisine: European, Eastern European
Ingredients: 1.5-2 tablespoons olive oil; 1 large onion (halved and sliced into half moons); 1 teaspoon salt; 1 lb cremini button mushrooms (sliced, 500 grams); 1 tablespoon olive oil; ½ teaspoon salt; 2 tablespoons butter; 2 teaspoon Dijon mustard; 2 cloves garlic; ½ teaspoon ground black pepper; 1.5 cups vegetable stock; 1.5 tablespoons flour (gluten-free or regular); 2 tablespoons water (or stock for slurry); 3 cups cooked brown lentils (canned or cooked at home, strained); ⅔ cup sour cream (light can be used); Parsley for garnish; Extra salt to taste