Preheat your oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper.

Heat 1 cup of whole milk in a small saucepan until boiling, steep with 2 black tea bags for 10 minutes, then cool.

Combine ½ cup all-purpose flour, ½ cup granulated sugar, and a pinch of salt in a medium bowl; cut in ¼ cup cold butter until crumbly.

In a large mixing bowl, whisk together 2 cups all-purpose flour, 2 teaspoons baking powder, ½ teaspoon baking soda, and ½ teaspoon salt.

In another bowl, whisk 1 cup sour cream, 2 eggs, 1 teaspoon vanilla extract, and cooled chai-infused milk until smooth.

Gently stir wet ingredients into dry ingredients until just combined to form a smooth batter.

Pour half of the batter into the baking pan, sprinkle with half the streusel mixture, add remaining batter, and top with remaining streusel.

Bake for 60-65 minutes until a toothpick comes out mostly clean, then cool in the pan for 10 minutes.

Transfer the cake to a wire rack, cool completely, then drizzle with a glaze of powdered sugar and milk.