In a small sauce pan, cook together the condensed milk and all-purpose cream in low to medium heat.
Add in a teaspoon of lemon juice into the milk and cream mixture and cook until it becomes thick. Cool and cover with plastic wrap then put inside the refrigerator to chill. Then beat the chilled cream mixture until it aerates or double in size. Set aside.
Mix happy mug caramel cake mix according to package instructions. Mix well.
Microwave for 1 minute and 30 seconds. Remove from microwave, be careful container will be hot.
Remove mug cake from the container to cool down and then slice cake crosswise in the middle to have 2 cake layers. Set aside. For later use.
In a small pan, cook mango cubes together with the caramel sauce (or may use the chocolate sauce instead included in the mix) for 3-5 minutes or until mango cubes slightly softened. Remove from heat and cool. Set aside.
To assemble the mini cake, get 1 layer of cake then spread a small amount of cream and half of the caramel mango cubes on top of the sliced cake. Place the second layer on top, pipe cream icing around the cake, top with the remaining mango cubes then garnish with fresh mint leaves.