In a large pot, combine the fennel seeds, star anise, peppercorns, apple cider vinegar, water, sugar, salt and orange peel.
Bring to a boil, stirring until the sugar and salt dissolve completely.
Reduce the heat and simmer for 5 minutes to infuse the aromatics.
While the brine simmers, thinly slice the fennel bulbs using a mandoline or sharp knife.
Place the sliced fennel into clean, sterilised jars.
Pour the hot brine through a fine mesh sieve over the fennel, ensuring it is fully submerged.
Run a spoon around the inside edge of each jar to release any trapped air bubbles.
Seal the jars tightly and let cool to room temperature.
Refrigerate for at least 24 hours before serving to allow the flavours to develop.
The pickled fennel will keep refrigerated for up to 2 weeks.
