In a medium-sized jug or bowl that can hold at least 4 cups of liquid, add in 120g (½ cup) of milk and sprinkle over the gelatin powder. Stir well and set aside to bloom.
In a medium saucepan, combine the remaining 120g (½ cup) of milk, heavy cream, sugar, and vanilla. Stir and gently heat the mixture over a low heat until it just begins to bubble. As soon as you see bubbles forming, remove the saucepan from the heat. Let it cool for 5 minutes (see note 1).
Carefully pour the cream/milk mixture into the bloomed gelatin while continuously whisking. Keep whisking for a few minutes until the gelatin is fully dissolved. If using vanilla pods, I recommend straining the mixture through a fine sieve after the gelatin has dissolved before proceeding to the next step.
Place the jug/bowl over ice cold water and stir every 5-10 minutes until the mixture is slightly cold to the touch and slightly thickened (see note 2).
Very lightly grease four 3.5 inch (or 6 ounce) ramekins with unflavored vegetable oil. Pour the mixture evenly into the ramekins (see note 3). Tap the ramekins lightly on the counter to get rid of any air bubbles. Tightly cover the tops with cling wrap and refrigerate for at least 4 hours, ideally overnight, to set.
Once set, run a sharp knife around the top edge of the ramekin to break the seal. Dip the ramekin into hot water for a few seconds, ensuring no water gets inside. Lift it out, wipe the bottom dry, then place a saucer over the top and invert the ramekin. Give it a gentle shake, and the panna cotta should slide out. If it doesn’t release after a few shakes, dip it back into the hot water for a few more seconds and try again (see note 4 if there is excess liquid after unmolding).
Place some of the berry sauce on top and serve. Enjoy!