Heat a little oil in a medium frying pan and cook bacon until brown. When cooked, place the bacon on absorbent paper and cool. Dice the bacon into tiny pieces and put them aside for later.
Finely slice the spring onion and grate the cheese. Put these aside.
Next, prepare the wet filling. In a medium bowl (or jug) mix the heavy cream, milk, and eggs until well combined, season with salt and pepper.
Preheat oven to 220°C (425°F). Lightly grease the insides of the mini muffin tin.
If your puff pastry comes unrolled, you will need to roll it out thin before cutting into rounds. Use a round cookie cutter to cut circles of dough to line the insides of the mini muffin tins.
Place the rounds in the cups of the prepared muffin tin. Carefully push the pastry to the bottom of the cups and gently press the pleated pastry to the sides. The pastry should be level with the top of the muffin tin. Note: You don't need to blind bake the pastry before adding the filling.
Divide the onions, bacon, and cheese evenly between the pasty-lined muffin cups.
Carefully pour the creamy egg filling into each of the muffin cups. The liquid should be level with the top of the muffin tin.
Place in the preheated oven and bake for 20 minutes or until golden brown.
Remove from the oven and allow to stand in the tins for about 5 minutes before transferring to a wire rack.
Serve warm or at room temperature.