To start, you'll need to combine cold milk and Agar-Agar (or gelatin) in a small saucepan and bring it to a boil. Once it is boiling, remove the pan from the heat and let it cool to a warm temperature. This step allows the Agar-Agar or gelatin to dissolve completely, creating a smooth base for your mousse.

While your milk mixture is cooling, you can begin making the cream. Using an electric mixer, blend together sugar and sour cream until they're well combined and the sugar has dissolved. This process should result in a creamy, smooth texture.

Next, add heavy whipping cream, a dash of sea salt, and a generous amount of vanilla to the sugar and sour cream mixture. Mix these ingredients together until they're well combined.

With the mixer set to low, slowly pour in the warm milk and gelatin mixture. Continue mixing for a few more minutes. At this point, the mixture should be quite liquid, similar to buttermilk, but it will start to thicken quickly as it cools.

Now, it is time to assemble your dessert. Tilt 8 oz round-bottomed glass cups slightly to the side on a serving platter, using a towel to support them.

Pour ¼ cup of the vanilla mousse into each cup, then place the entire platter into the fridge to cool and set. This angled presentation adds an elegant touch to your New Year's Eve dessert.

For the berry jello puree, combine berries (either frozen or fresh) with sugar and water in a medium saucepan. Bring this mixture to a boil, then reduce the heat to low and let it simmer for about 5 minutes, stirring occasionally. Once done, remove it from the heat and let it cool.

Once the berry mixture has cooled to a warm temperature, transfer it to a food processor and process it until it becomes smooth in texture.

In a separate bowl, combine ¼ cup sugar with Agar-Agar or gelatin. Stir this mixture into the warm berry puree, then bring it back to a boil. Let it simmer for a minute, then remove it from the heat and let it cool to a warm temperature.

Pour the berry jello puree over the vanilla mousse in each glass cup, maintaining the tilted position. Return the cups to the fridge to set.

Once the vanilla mousse and berry jello puree have been completely set, fill the glass cups with fresh berries. For a touch of extra color and presentation, consider placing a whole strawberry, green stem intact, or a mint leaf on top of each dessert.

These desserts can be enjoyed immediately or stored in the fridge until you're ready to serve them.

For the best flavor and texture, remove the cups from the fridge 30 minutes before serving to allow the mousse and berries to come to room temperature. Enjoy your delicious New Year's Eve dessert!