Prepare Molds: If you plan to unmold the panna cotta onto plates, lightly grease the inside of the glasses with vegetable oil and use a paper towel to wipe out most of the oil, leaving only a light residue. Otherwise, you can leave them uncoated.
Soak Gelatin: Soak the gelatin sheets in cold water until soft. Set aside.
Heat Mixture: In a medium saucepan, heat the whole milk, heavy cream, and granulated sugar until it reaches a simmer (do not boil). Remove from the heat.
Add Gelatin: Squeeze the gelatin to remove any excess water and add it to the pan, stirring constantly until the gelatin is fully dissolved.
Steep Tea: Add the vanilla extract and loose leaf Earl Grey tea. Allow the mixture to steep for 10-15 minutes.
Strain Mixture: Strain the mixture through a fine sieve to remove the tea leaves. Pour evenly among the prepared molds.
Refrigerate: Refrigerate until set, for at least 4 hours or overnight.
Unmold and Serve: To remove from the mold, dip the bottom of the mold into a pot of hot water for 5 seconds to loosen the panna cotta. Slide a knife around the edge, then carefully turn over onto a serving plate.