Preheat the oven to 240°C/ Fan 220°C/Gas 9 and line a large baking sheet with baking parchment.
Dust a clean surface with flour. Roll out the pastry to make a square approximately twice the length of one rasher of bacon and 2-3mm thick. Cut the pastry into four equal squares.
Transfer the pastry squares to the lined baking sheet. Imagine the squares are diamonds and place two pieces of bacon across each piece of pastry, orienting them from tip to tip.
Sprinkle the grated cheese evenly over the bacon rashers and place a tomato slice 2cm in from the ends of each rasher of bacon.
You now have two untouched corners of pastry on each square. Fold one into the middle without stretching it – just over and beyond the filling.
Brush the top of that folded pastry with a little milk, then fold the remaining corner over and onto the top of it. Repeat with the other three squares.
Brush all the exposed pastry with more milk. Bake towards the top of the oven for 16-18 minutes, until the pastry is puffed and golden, and any exposed bacon crisp.
Remove the slices from the oven and brush all the surfaces with maple syrup and leave to cool for 5 to 10 minutes before serving.