Cook quinoa with apple, cinnamon stick, and 1 ½ cup water, over medium heat for 15 minutes or until soft. Let cool. Strain, reserving the cooking liquid, and measure 1 cup of quinoa with apples.
Preheat the oven to 375ºF.
In a saucepan over medium heat, melt sugar with 2 tablespoons water, and cook over high heat until lightly golden.
Turn off the heat and pour a small amount of caramel in six ramekins, or one round cake pan (be careful, the caramel is extremely hot and may cause bad burns in the skin).
In the blender, process quinoa, eggs, sweetened condensed milk, unsweetened evaporated milk, vanilla, and 1/2 can of the reserved cooking liquid.
Pour in the ramekins and accommodate all in a large baking pan, with at least a 2-inch rim because we are adding 1 inch hot water, so the flans can bake in a water bath.
Bake for 40 minutes.
Turn off the oven, take out the flans, and let them cool at room temperature. Chill overnight.
Unmold and garnish with whipped cream, fruits, and mint leaves.