Brew the Earl Grey Milk: Heat 1/2 cup whole milk in a small saucepan until steaming, not boiling. Add 3 Earl Grey tea bags, steep for 10 minutes, then remove tea bags and let milk cool completely.

Make the Crust: In a bowl, mix graham cracker crumbs, melted butter, and sugar until it looks like wet sand. Press into the bottom of a 9-inch springform pan lined with parchment paper. Chill while preparing the filling.

Make the Cheesecake Batter: In a large bowl, beat cream cheese until smooth and fluffy. Add 3/4 cup sugar and mix until combined. Mix in sour cream, heavy cream, and cooled Earl Grey milk. Add eggs one at a time, mixing gently between each addition.

Bake the Cheesecake: Pour batter into the prepared crust. Tap the pan gently to release air bubbles. Place in a baking tray filled with hot water and bake at 325°F (160°C) for 50 minutes. The edges should be set, and center slightly jiggly. Turn off the oven, crack the door, and let cool inside for 1 hour.

Make the Mulberry Sauce: In a small saucepan, combine mulberries, sugar, and lemon juice. Cook over medium heat until soft and bubbling. Stir in cornstarch mixed with water and simmer until thickened. Let cool completely.

Chill and Top the Cheesecake: Refrigerate cheesecake for at least 4 hours or overnight. Before serving, spoon the cooled mulberry sauce on top.