Whisk the flour, tea, malted milk powder, and salt together in a small bowl. Set aside.
Put the butter, a 1/4 cup (30 g) of the confectioners’ sugar, and the orange zest in the bowl of a stand mixer fitted with the paddle attachment. Mix on medium speed until pale and fluffy, about 3 minutes. Reduce speed to low and gradually add in the flour mixture until just combined.
Shape the dough into a log 1 1/4 inches in diameter, and wrap tightly in cling film or parchment paper. Freeze until firm, about 1 hour.
Preheat the oven to 350 °F (180 °C). Cut the log into 1/4-inch-thick slices. Space 1 inch apart on a baking sheet lined with parchment paper.
Bake the cookies, rotating the sheet halfway through, until the edges are golden, about 15 minutes. Let cool on the sheet.
In a small bowl, mix the remaining 1/4 cup (30 g) of confectioners’ sugar with the orange juice using a spoon or fork. Drizzle the glaze over the cooled cookies, let dry for 5 min before serving.
The cookies can be kept for up to 5 days in a sealed container.
This recipe works great with chai instead of Earl Grey, and you can vary the liquid in the glaze also, for example by using almond extract diluted with a bit of water.