Cut the cream cheese into small cubes. Let sit at room temperature when preparing other ingredients.

In a medium saucepan, combine milk and heavy cream. Cook over medium heat. Bring mixture just to a simmer (175˚F), about 5 minutes, stirring often. Add sugar and stir until dissolved. Remove from heat.

Transfer the beaten eggs into a medium mixing bowl. While whisking the eggs, slowly pour in a little bit of hot cream. Whisk to mix and add more. Whisk again. Pour in about half of hot cream. Then whisk the yolk mixture back into the pot with the cream. Return the pot over medium heat and cook until the mixture is thick enough to coat the back of a metal spoon (at least 160˚F), stirring constantly. Remove from heat.

Whisk in cream cheese until smooth. Stir in lemon juice and vanilla extract. Strain the ice cream base through a fine mesh sieve into an airtight container. Cool mixture at room temperature for 15 minutes. Press a piece of plastic wrap onto the surface of the custard. Transfer to an airtight container and chill in the fridge for at least 4 hours or overnight.

Meanwhile, prepare the guava jam. Cut the paste into thin slices. Add to a small saucepan with the water. Cook over medium heat until the paste has dissolved. Reduced heat if needed. It should look like a thick jam. If the jam is too thick, add a little bit more water. If your jam tastes too sweet, add a little bit of lemon juice. Transfer to a heat proof container and chill in the fridge for at least 2 hours.