Preheat oven to 425°F.
Pour entire can of condensed milk into a square glass baking dish and cover with foil. Place in oven and bake for 1.5 hours to 2 hours or until it reaches a caramel color.
Remove from oven and let cool for 5 minutes. After cool period, whisk dulce de leche until lumps disappear. Store in airtight container in fridge for up to 2 weeks.
Scoop 1 to 2 tbsp of dulce de leche into a bowl. Allow to rest on kitchen counter until it reaches room temperature (2 to 3 hours). Note: Skip this step if your dulce de leche is already at room temperature.
Begin by frothing 1/2 cup of desired milk and set aside while you prepare the espresso.
Scoop 1 tbsp of dulce de leche into espresso cup. Brew espresso into the cup with the dulce de leche. Stir the dulce de leche mixture and espresso thoroughly until completely smooth. Stirring quickly helps.
Pour the espresso mixture into your choice of serving mug or glass following by the frothed milk and stir gently. For iced lattes, you'll pour cold milk over the espresso mixture followed by 2 to 3 ice cubes.
Lastly, top with dark chocolate whipped cream (see link above in post) or freshly whipped creamed and dust lightly with ground cinnamon for color.