Preheat the oven to 190°C, 170°C fan, 375°F, gas 5. Start with the filling. Heat the olive oil in a frying pan, add the onion and cook gently for 5 minutes, until beginning to soften. Add the beef and carrots and the thyme, if using. Turn up the heat and cook for a further 5 minutes, until the beef is browned. Set aside to cool completely.
While the filling cools, unroll the pastry on a lightly floured board and cut out 6 rounds with a plain, 11cm (4.5 in) biscuit cutter. Reroll the scraps of pastry and cut out 2 more rounds to make a total of 8. Space out on a baking sheet lined with nonstick baking paper and chill in the fridge for 10 minutes.
Place a heaped tablespoon of filling on one side of each pastry round. Paint a little beaten egg around the edge with a pastry brush. Fold the pastry over to form a semi-circle, pressing the edges together firmly. Use a fork to crimp the edges or pinch them between thumb and finger to form a pattern, if liked. Cut a small slit in the top of each pasty. Repeat until all 8 pasties are made. At this point the pasties may be chilled for up to 24 hours or frozen for up to 3 months. Before baking, paint the pasties with egg to glaze. Bake for 15-20 minutes, until golden brown and puffed up. To make the salsa, combine all the ingredients. Season to taste. Eat the pasties warm or cool, with the salsa.
Tip: Half a teaspoon of 5-spice powder added to the pan with the beef makes a very nice substitute for the thyme leaves, but only add it if your little ones are keen on exotic flavours.
See more Beef recipes
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.