Preheat the oven to 170°C fan bake. Lightly grease a standard 12-hole muffin tin and brush with a little melted butter.
Cut the filo pastry into squares large enough to line the muffin cups.
Working with one piece at a time, layer six sheets into each muffin cup, alternating the angles to create a basket shape.
In a bowl, combine the diced chicken, cream cheese, sour cream, lemon juice, spinach, onion powder, and garlic powder. Mix until well combined.
Spoon approximately 1 teaspoon of the chicken mixture into each filo case.
Add approximately ½ teaspoon of cranberry sauce to each tart.
Top with another small spoonful of the chicken mixture.
Place two small pieces of camembert on top of each tart.
Brush the exposed filo pastry edges with the remaining melted butter.
Bake for approximately 20 minutes, or until the pastry is golden and crisp and the filling is bubbling.
If the filo begins browning too quickly, loosely cover with foil during the final few minutes of cooking.
Allow the tarts to cool slightly before carefully removing from the muffin tin. Serve warm or cold.