This halved batch makes about 48 apparently, but I'd make them bigger and have fewer next time.
140g plain flour
1/4 tsp salt
30g icing sugar (I was a bit like o__O over this, so I added a tbsp or so of caster sugar too. Okay, sugar junkie, but whatever)
1/2 tbsp orange zest
1. Whisk flour, tea, and salt in a small bowl; set aside.
2. Put butter, sugar, and orange zest in the bowl of an electric mixer fitted with the paddle attachment. Mix on medium speed until pale and fluffy, about 3 minutes. Reduce speed to low; gradually mix in flour mixture until just combined.
3. Transfer dough to a piece of baking paper and shape into a log. Roll in baking paper to 1 1/4 inches in diameter (*COUGH* OR BIGGER, IF YOU CAN'T JUDGE MEASUREMENTS), prsesing a ruler along edge of parchment at each turn to narrow the log and force out air. Put it on a level baking tray in the freezer until firm, 1 hour (ppft. Half an hour. Impatient, remember?).
4. Preheat oven to 180C. Cut logs into 1/4-inch-thick slices. Space 1 inch apart on baking sheets lined with parchment. They don't spread, by the way.
5. Bake biscuits, rotating sheets halfway through,until edges are golden, 13 to 15 minutes. Let cool on sheets on wire racks. They can be stored in airtight containers at room temperature up to 5 days.