Quick and Simple Slow Cooked Steak Diane Casserole

The Simple Slow-Cooked Steak Diane Casserole is a modern twist on the classic Steak Diane, transforming it into a hearty casserole that melds the rich flavors of the traditional dish with the ease and convenience of slow cooking. This casserole version features tender pieces of steak simmered in a flavorful mushroom and mustard sauce, enriched with the subtle hint of brandy or Worcestershire sauce. Perfect for a comforting family dinner or as a gourmet meal for gatherings, this dish brings the essence of a fine dining experience into the coziness of your home, with the slow cooker doing most of the work.

Inspired by a memorable steak Diane enjoyed at a quaint bistro, the challenge was to recreate the dish’s sophisticated flavors in a more accessible, family-friendly format. After experimenting with various ingredients and cooking methods, the Slow-Cooked Steak Diane Casserole emerged as a standout, capturing the essence of the original while offering the warmth and heartiness of a casserole. The first time it was served at a family dinner, it was greeted with enthusiasm and delight, sparking conversations about the origins of the dish and the creativity behind transforming classic recipes for the modern table.

This casserole has since become a cherished recipe, symbolizing the joy of sharing good food and creating new traditions from old favorites. It’s a testament to the power of cooking to bring people together, offering a delicious way to enjoy classic flavors with minimal effort.

Why You’ll Love Simple Slow-Cooked Steak Diane Casserole
Rich and Flavorful: Enjoy the luxurious taste of Steak Diane in a hearty, comforting casserole.

Effortless Preparation: The slow cooker simplifies the cooking process, making gourmet flavors accessible on any night.
Versatile: Easily adaptable to your taste preferences and perfect for any occasion, from casual dinners to special celebrations.
Make-Ahead Convenience: Ideal for preparing ahead of time, allowing the flavors to deepen and meld together beautifully.
Ingredients Notes For Simple Slow-Cooked Steak Diane Casserole
Steak: Use tender cuts such as sirloin or ribeye, cut into bite-sized pieces for easy eating.
Mushrooms: Sliced mushrooms add earthiness and texture to the sauce.
Mustard and Worcestershire Sauce: Provide the tangy, umami-rich backbone of the Diane sauce.

Brandy: Adds depth and a traditional flavor to the sauce, though it can be substituted with additional Worcestershire sauce or beef broth for a non-alcoholic version.
Cream: Enriches the sauce, making it silky and luxurious.
Garlic and Onions: Form the aromatic base of the casserole, enhancing its savory notes.
Recipe Steps
Brown the Steak: Lightly brown the steak pieces in a skillet before adding them to the slow cooker to enhance their flavor.
Sauté the Aromatics: In the same skillet, cook the onions and garlic until softened, then add the mushrooms until they release their moisture.
Deglaze: Add brandy (or substitute) to the skillet, scraping up any browned bits for extra flavor.

Combine Ingredients: Transfer the steak, aromatics, and mushrooms to the slow cooker. Stir in mustard, Worcestershire sauce, and beef broth.
Slow Cook: Cover and cook on low for 6-8 hours, until the steak is tender.
Finish the Sauce: Stir in cream during the last 30 minutes of cooking to thicken the sauce.

Serve: Adjust seasoning with salt and pepper. Serve the casserole hot, garnished with fresh parsley or thyme.
Storage Options
Refrigerate: Store leftovers in an airtight container for up to 3 days.
Freeze: Freeze in suitable containers for up to 1 month. Thaw overnight in the refrigerator before reheating gently.



  • Beef steak: 2 lbs (about 900g), cut into bite-sized pieces (sirloin or tenderloin works well)
  • Salt and pepper: to taste
  • Olive oil: 2 tablespoons, for searing
  • Onion: 1 large, finely sliced
  • Garlic: 2 cloves, minced
  • Mushrooms: 8 oz (about 225g), sliced
  • Beef broth: 1 cup
  • Dijon mustard: 2 tablespoons
  • Worcestershire sauce: 1 tablespoon
  • Brandy or cognac: 1/4 cup (optional, can substitute with additional broth if preferred)
  • Heavy cream: 1/2 cup (to be added at the end)
  • Fresh parsley: chopped, for garnish


Prepare the Beef:
Season the beef steak pieces generously with salt and pepper.
In a skillet over medium-high heat, heat the olive oil. Sear the beef in batches until browned on all sides but not cooked through. Transfer the browned beef to the slow cooker.
Sauté the Vegetables:
In the same skillet, add a bit more oil if needed. Sauté the onion and garlic until soft and translucent, then add the mushrooms and cook until they’re browned and their moisture has evaporated.
Deglaze and Combine:
Add the brandy or cognac to the skillet to deglaze the pan, scraping up any browned bits from the bottom. (If not using alcohol, skip to the next step.)
Transfer the onion, garlic, and mushrooms mixture to the slow cooker over the beef. Stir in the beef broth, Dijon mustard, and Worcestershire sauce.
Slow Cook:
Cover and cook on low for 6-8 hours, or on high for 3-4 hours, until the beef is tender.
Finish the Sauce:
Once the beef is tender, stir in the heavy cream. Adjust the seasoning with more salt and pepper if needed. If the sauce is too thin, you can thicken it by mixing a tablespoon of cornstarch with 2 tablespoons of water and stirring it into the casserole. Let it cook for an additional 15-20 minutes on high if using the cornstarch slurry.
Serve the Steak Diane Casserole garnished with chopped fresh parsley. This dish goes well with mashed potatoes, rice, or a simple green salad.

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