Season the beef with salt and pepper. Heat the olive oil in a frying pan over a medium-high heat and sear the beef with the thyme until browned on all sides.
Add the onion and garlic, cook for 2-3 minutes, then add the beer and simmer for a further 2-3 minutes.
Add the stock, sweet potato and carrots, ensuring they are covered with liquid, and simmer for 20 minutes until the sweet potato is soft. The should beef be tender, so do a taste test and if it's still too chewy-continue cooking for a few more minutes.
Add the mustard and cornflour, and stir until the mixture thickens. Season to taste with salt and pepper and remove from the heat.
Preheat the oven to 200°C and grease a medium-sized ovenproof dish (about 20 x 20 cm).
Layer three sheets of phyllo pastry, cut the pile in half with a knife and cover with a damp kitchen towel to prevent the pastry from drying out.
Spoon the beef mixture into the dish and cover with layers of pastry, brushing each one with the beaten egg before adding the next sheet.
Bake in the middle of the oven for 15 minutes until the pastry is crispy and golden.Note:
Any cut of beef will do, but the better the cut, the more tender the end result.Reprinted with permission of Sarah Graham. To read more recipes, click here.