Au poivre sandwich sauce: combine all sauce ingredients in a medium bowl and whisk to combine fully.

Store in a sealed container in the refrigerator for up to 2 weeks.

Steak patty: slice 3 to 4 ounces of sirloin or ribeye steak very thinly and then slice those thin pieces into strips and turn the strips to slice those into small pieces. The goal here isn't minced steak, but to create small pieces. 

On top of a small piece of parchment form the steak pieces into a patty. I use a 4-inch biscuit round, but you can just use your hands to form a roughly circular patty on top of the piece of parchment paper. 

Freeze the patty on top of the parchment for at least 2 hours. The easiest way to do this is to add the parchment on top of a sheet pan to the freezer. Once it's fully frozen if you formed extra patties, add them to a ziptop bag with the parchment piece still attached to the bottom of the patty. 

Spinach and mushrooms: this step can be done well in advance if you want. You need to cook the spinach and mushrooms until they are a little bit soft so that they will be cooked and ready for the omelet.

You can cook both mushrooms and spinach in the same pan or you can cook them in separate pans. That is up to you. They both will cook for about 5 minutes over medium heat. Dust both with salt and pepper while they are cooking in a teaspoon of oil. I also like to add a little minced garlic and a pinch of red pepper flakes to the spinach. Once they are cooked remove them to a plate if you are planning to sandwich them right away, or to a sealed container in the refrigerator for later. 

Back to the steak: when you are ready for a sandwich, add 2 tablespoons of olive oil to a medium pan over medium-high heat. When the oil is hot and shimmering, add 1/4 to 1/8 teaspoon of ground black pepper and a pinch of salt to the shimmering oil. Place the steak patty right on top of the salt and black pepper. Cook the steak patty for 4 to 5 minutes per side. While the first side is cooking, season the second uncooked side with a good sprinkling of ground black pepper and a pinch of salt. Once the steak is cooked, move it to a plate or cutting board to rest.

Folded egg: if you're using the same pan that you cooked the steak in, remove it from the heat and wipe it out really well to remove any cooked bits. Break one whole egg into a small bowl and whisk to combine fully. Add salt and pepper to the egg to season. Add the pan (or a new pan) back to medium-low heat and add a tablespoon of butter.

Sprinkle your cooked spinach and mushrooms around the butter. Try to keep things spread out a little.

Once the butter is bubbly and melted, pour your whisked egg on top of the butter and vegetables. Immediately start letting the egg spread out on the bottom of the pan so that it all starts to cook. While it is cooking, you can help it out by keeping the egg in a round or square-ish shape and tilting the pan to allow the runny egg on top to roll off and touch the pan itself. Try to keep the shape somewhat consistent. This will help with folding.

Once most of the egg is set (after 1 to 2 minutes) you can start to fold. Using a spatula, attempt to scoop up one side and fold it over the other. This isn't always easy to do, and it doesn't really matter if you mess it up. But you effectively want to fold everything over itself once or twice until the egg is folded into a size that is consistent with your sandwich. 

Move the fully cooked folded egg omelet to a plate to start sandwich assembly.

Sandwich assembly: add au poivre sauce to the bottom bagel slice if you like your sandwich extra saucy. Place your steak patty on top of the bottom bagel slice.

Add your spinach and mushroom folded egg on top of the steak patty. 

Add a spoonful or two of au poivre sauce to the top bagel slice and then place that on top of the sandwich to complete. 

Serve and enjoy.