Preheat oven to 350 degrees. Butter an 8-inch round cake pan and line with parchment paper.
Combine all-purpose flour, baking powder, tea, and salt in a medium mixing bowl. Keep it aside.
In a large mixing bowl, beat the butter and sugar with an electric mixer on medium speed for 3 minutes, or until light and fluffy.
Add orange zest and beat to combine.
Add eggs, one at a time, beating well after each addition, scraping sides of the bowl as necessary.
At low speed, beat in the flour mixture ( all purpose flour, baking powder, tea, salt) until just mixed. (Be careful not to overmix.)
Add the milk in to batter and beat until just combined.
Add chopped chocolate and fold it into the batter using a spatula.
Pour the batter into the prepared pan. Smooth the top of the batter in the pan.
Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out moist.