Preheat oven to 425°F

Step 1: Place potatoes in a saucepan (or a pot big enough to fit) and cover with cold water and turn heat to high. Boil potatoes until a fork easily goes through and they are soft (about 20 minutes)- drain and let cool, then slice into 1/4″ slices.

Step 2: In a large skillet over medium heat, add olive oil, onions and mushrooms. Saute until all of the water cooks out and both the onions and mushrooms start to take on a caramelized brown color – this takes about 20 minutes, stirring occasionally. Transfer mushrooms and onions to a plate to rest. 

Step 3: In the same skillet, add the ground beef and cook until browned and cooked through and you no longer see any pink (ground beef is hard to get a temperature on). Add the mushrooms and onions back into the skillet and sprinkle in the flour, salt, garlic powder, pepper and stir in the dijon mustard. Stir until you no longer see any white from the flour. 

Step 4: Start pouring in the milk, 1 cup at a time until it starts to thicken. When it warms up, the flour will help the sauce get thick. When all the milk has been poured in and the sauce becomes a gravy consistency, stir in half of the shredded cheese and turn off the heat. 

Step 5: Place the sliced potatoes into a 9×13 baking dish in an even layer on the bottom (it’s okay if they are on top of each other). Pour the beef, mushroom, onion, gravy mixture on top of the potatoes. Sprinkle the remaining cheddar cheese on top evenly. 

Step 6: Place in preheated oven for 15 minutes or until the cheese is bubbly and brown on top

Garnish with fresh herbs when the stroganoff comes out of the oven.