In a small microwaveable bowl combine the guava nectar and one packet of gelatin. Stir to combine and allow to sit for 10 minutes.

Place the fully thawed blueberries in the blender and blend to fully puree. The required amount is 1 1/2 cups of puree. Add more berries if needed to yield 1 1/2 cup.

Place the bowl with gelatin in the microwave for 1 minute. Stir the gelatin mixture. Combine the gelatin and puree in a large liquid measuring cup to make pouring easy. Stir to fully combine.

Place the tumblers on their side in the cavities of a mini muffin tin (refer to photo). Gently pour the gelatin mixture into each container until the liquid is almost at the edge of the glass. Place into the refrigerator and allow to chill until firm; approximately 2 hours.

In a small bowl combine 1/2 cup of the milk and the second packet of gelatin. Stir to combine and set aside for 10 minutes.

In a heavy, medium size saucepan, combine the remaining 1/2 cup of milk, cream, and the sugar. Over medium-low heat stir the mixture constantly to fully dissolve the sugar and heat the liquids (should not simmer or boil). Add the gelatin mixture, whisking it together until the gelatin have dissolved into the liquid. Remove from heat and stir in the vanilla extract and lime zest.

Remove the containers from the refrigerator and set them upright on a small baking sheet. Pour the cream mixture into a large liquid measuring cup (to ease pouring into the containers).

Pour the cream mixture into the containers until it almost reaches the top and meets the top most point of the blueberry-guava gelatin making a geometric pattern.

Place the baking sheet into the refrigerator and allow the panna cotta to fully set; about 4 hours.