In a small mixing bowl, whisk milk and cornstarch to form a lump-free slurry. Set aside until ready to use.
In a wide heavy bottom pan (non-stick is preferable), combine evaporated milk and heavy cream. Bring to a boil on medium flame, stirring the milk frequently to avoid burning or scorching the bottom. Simmer for 2~3 minutes.
Lower the flame to medium-low and slowly stir in the cornstarch mixture. Cook for 3-4 minutes, stirring frequently. Mixture will be slightly thick at this point.
Next add sugar and mango puree. Let the mixture come to a slow simmer and cook for 3~4 minutes. Stir in ground cardamom, mix well and turn off the heat. Let the mixture cool completely.
Pour into kulfi or popsicle molds or into a wide glass dish*. Freeze until set for about 4~6 hours or overnight.
When ready to serve, remove the molds from the freezer and briefly run them under hot water to unmold and serve immediately.