Preheat oven to 375°F (190°C) and line a muffin tin with paper liners.
In a bowl, whisk flour, sugar, baking powder, baking soda, salt, and all spices.
In another bowl, beat eggs, oil, milk, vanilla extract, and brewed chai tea.
Pour wet ingredients into dry ingredients and mix until just combined.
Divide batter evenly into muffin cups, filling about ¾ full.
Sprinkle brown sugar on top if using.
Bake for 18–20 minutes until golden and a toothpick inserted comes out clean.
Cool in the pan for 5 minutes before transferring to a wire rack.