Prepare all the fresh produce first. Slice the onion, chop the garlic roughly and slice the clean mushrooms. Keep each separately aside.
1 Onion, 2 clove Garlic, 16 ounces Mushroom
Place your Dutch oven on the stove and heat the oil and melt the butter.
1-2 Tablespoon Oil, 1 Tablespoon Butter
Stir in the onion. Sauté until lightly soft and keep over a medium-high heat setting.
1 Onion
Add the garlic and stir-cook slightly for a minute over a medium heat setting.
2 clove Garlic
Stir in beef cubes and cook them briefly on all sides to brown them a bit. Keep a higher heat setting.
1 pound Beef Cubes
Mix in the sliced mushrooms. Cook down a bit so that the water from the mushrooms is released.
16 ounces Mushroom
Season with bay leaf, grated nutmeg, salt, crushed black pepper and the mustard paste. Mix it all in.
pinch Nutmeg, 1 Bay Leaf, ¼ Teaspoon Salt, ⅛ Teaspoon Black Pepper, 1 Tablespoon Dijon Mustard
Keep on the same higher heat setting and deglaze by pouring in white wine and the beef broth. Combine everything well.
1 cup White Wine, ½ cup Beef Broth
Reduce the heat setting to a medium-low and stir in the sour cream. Mix well into the dish.
1 cup Sour Cream
Cover the Dutch oven with the lid and keep the stove heat on a lower heat setting.
Simmer the beef stroganoff on the lower heat setting, covered, until the meat is tender and falling off. This can take 1½ - 2 hours depending on your meat quality.
When the meat appears cooked and tender, take out the bay leaf and discard it. Keep on the lowest heat setting.
Prepare the slurry by combining the all-purpose flour with the lukewarm water. Make sure no lumps are left and that it is smooth.
1 Tablespoon All-purpose Flour, 2 Tablespoon Lukewarm Water
Pour a tablespoon of the beef stroganoff sauce into the slurry, so that the temperature is gradually matched. Then pour all the slurry into the beef stroganoff sauce and mix it all well. The sauce will turn velvety thick.
Take the dish from the heat source and serve up hot.