1. Sprinkle the beef with salt and pepper.
2. Using 1 tbsp of the oil, brown the beef (in batches if needed) in a large skillet on medium-high heat for 8-12 minutes. Set aside.
3. Using the remaining 1 tbsp of oil, cook the onion and garlic in the same pan on medium heat until softened, 2-3 minutes.
4. Add the mushrooms and cook for 2-3 minutes until softened.
5. Add the flour, stirring continuously for 30 seconds (it will form a lumpy paste).
6. Follow either the slow cooker or stovetop method below.

Slow cooker method

1. Add tomato paste, paprika, Worcestershire sauce and beef stock to the slow cooker and stir to combine.
2. Add the cooked beef and mushroom mixture and stir gently to combine. The beef may not be completely submerged, which is fine; it will melt into the sauce as it cooks.
3. Cook on high for 4 hours or on low for 8 hours. Stir in the sour cream for the remaining 15 minutes of cooking time. The beef should come apart easily with a fork. If not, cook in 15-minute intervals until soft.

Stovetop method

1. Return the beef to the pan and add the tomato paste, paprika, Worcestershire sauce and beef stock.
2. Return to a boil, then simmer on the lowest heat for 1.5 hours, lid on. Stir occasionally. If the sauce is sticking to the base of the pan, add 1/2 cup of water.
3. Remove the lid and cook for an additional 1 hour to thicken.
4. The beef should come apart easily with a fork. If not, cook in 15-minute intervals until soft.
5. Once the beef is soft and melting, stir through the sour cream to create a thick, creamy sauce.

Assemble pies

1. Preheat oven to 220°C/425°F (200°C fan).
2. Fill your bowls/ramekins with the stroganoff.
3. Cut the sheet of puff pastry into four even squares.
4. Lay the puff pastry straight on top of the bowls/ramekin, and using your fingers, crimp the pastry around the outside of the bowl.
5. Using a pastry brush, brush the tops of the pies with egg and sprinkle with sesame seeds and salt (optional).
6. Bake for 20 minutes or until pastry is golden and flaky.
7. Use oven mitts to remove the pies from the oven. Allow them to stand for 10 minutes before serving.