In a large bowl, using a hand-held mixer or stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium speed until completely smooth and creamy. Add the brown sugar and beat on medium-high speed until fluffy and creamy. Beat in the egg and vanilla extract on high speed. Scrape down the sides and bottom of the bowl as needed and continue to beat until fully combined.
In a separate bowl, whisk the flour, cinnamon, Tick Tock Organic Rooibos tea and salt together until combined. On low speed, slowly add into the wet ingredients until fully mixed in. The biscuit dough will be thick and sticky.
Switch to high speed and beat in the zest and orange juice. Turn the dough out onto a floured work surface and, with floured hands, divide in two. Shape each half into a 20cm log, about 6cm in diameter (the measurements don’t have to be exact).
Tightly wrap the logs in plastic wrap and chill in the fridge for at least 4 hours or up to 5 days. Chilling well is essential for this biscuit dough.
Pre-heat oven to 180°C. Line two large baking sheets with baking paper or silicone baking mats and set aside.
Take the dough out the fridge and slice each log into 12 equally thick biscuits and place on the baking sheets about 5cm apart.
Bake the biscuits for 12-14 minutes or until brown around the edges. Allow to cool for 5 minutes before transferring to a rack to cool completely.
Melt the chocolate in a bain-marie until smooth.
Dip each biscuit halfway into the chocolate and place onto a parchment-lined baking sheet. Sprinkle with sea salt and orange zest (if desired). Place the baking sheet into the refrigerator until the chocolate has set.