Preheat the oven to 180ºC, fan 160ºC, gas 4. Put the butter, sugar and syrup in a small heavy-based saucepan. Heat gently until the butter has melted, then stir and bring the mixture up to a simmer.
Remove from the heat and stir in the flour, ginger and lemon rind.
Drop spoonfuls of the mixture about 10cm apart on non-stick baking sheets. Bake in batches for 12 -15 minutes, until bubbling and deep golden.
Remove from the oven and cool for a few seconds. Lift the soft rounds off the tin and mould around a lime or small satsuma. When just set, lift the case off the fruit and place on a rack to set and harden completely. Repeat with all the mixture.
When ready to hang, cut a strawberry lace in half and lay on the work surface in a cross. Place the bauble at the centre of the cross and fill with popcorn. Gather the four shoe laces together and tie a knot at the top. Hang the bauble on the tree.