Steep 2 Earl Grey tea bags in 1 cup of hot milk for about 5 minutes. Remove tea bags and whisk in 3 tbsp Greek yogurt and 1 tsp vanilla extract until smooth.

Gently roast 1.25 cups of blackberries in a skillet over medium heat for 5–7 minutes until soft and fragrant. Mash lightly and cool.

Cream together 0.5 cup unsalted butter and 0.75 cup sugar until fluffy. Add 1 whole egg and 1 egg white, mixing until smooth.

In a separate bowl, whisk together 1.25 cups flour, 1 tsp baking soda, 0.25 tsp baking powder, and 0.25 tsp sea salt. Fold into wet mixture along with remaining tea leaves.

Swirl 0.25 cup cooled blackberries into the batter, then fill cupcake liners two-thirds full.

Bake in a preheated oven at 350°F for 19–21 minutes until a toothpick comes out clean. Cool in the pan for 10 minutes.

Strain leftover blackberries to collect 1 tbsp blackberry juice. Beat 4 oz cream cheese and 0.5 cup softened butter together, gradually adding 3 cups sugar and blackberry juice until fluffy.

Frost cooled cupcakes with the blackberry cream cheese frosting and drizzle remaining blackberry juice over them.