Place the cake flour, icing sugar and salt into a food processor. Add the block of butter and blend until the mixture resembles fine breadcrumbs.
Beat the egg, lemon juice and water together and pour into the processor. Blend until the pastry just comes together. Do not overwork it.
Divide into 2 pieces. One slightly bigger than the other. Wrap or cover and chill for 30 minutes.
Meanwhile, heat the butter. Add the onion, cranberries, sugar and spice. Simmer for +- 10 minutes. Stir occasionally. Cool to room temperature.
Preheat oven to 200 Degrees Celsius.
Roll the bigger portion of pastry out to cut out 12 x 10 cm circles. Grease a cupcake tray or patty pan and line with the pastry circles.
Fill each one with a heaped teaspoon of cooled cranberry filling, top with goat's cheese and a few thyme leaves.
Roll the smaller portion of pastry out to cut toppers for each pie: smaller circles, stars, leaves - whatever you like :-)
Brush the exposed pastry with egg and top with cut pie toppers. Brush with egg.
Bake for 12 - 15 minutes.
Grind sugar and thyme together until fragrant. Place in a sieve and sprinkle of the mince pies!
Serve warm or room temperature.