1. Prepare the can: Remove the label from the can of sweetened condensed milk. Place the can in a saucepan and fill with water so that the can is fully submerged, ensuring the water level is at least 2 inches above the top of the can.

2. Simmer the milk: Bring the water to a boil over medium-high heat. Once boiling, reduce the heat to low, allowing the water to simmer. Cook for 2-3 hours, ensuring the can remains submerged by adding water as needed.

3. Check the consistency: After 2-3 hours, carefully remove the can with tongs and allow it to cool. The condensed milk should have thickened and turned golden brown. For a darker and thicker version, cook for up to 4 hours.

4. Cool and open: Let the can cool completely before opening, as it may be under pressure.

Slow Cooker Method (Hands-Off Approach):

1. Prepare the can: Remove the label from the can and place it in the bottom of a slow cooker.

2. Submerge the can: Fill the slow cooker with water to cover the can by at least 2 inches.

3. Cook on low: Cover the slow cooker and cook on low for 8 hours. Check the water level occasionally, adding more water if necessary.

4. Cool and open: Once done, remove the can with tongs and allow it to cool completely before opening.

Oven Method:

1. Preheat the oven: Set your oven to 400°F (200°C).

2. Prepare the dish: Pour sweetened condensed milk into an oven-safe dish (a pie dish works well). Cover with aluminum foil.

3. Bake the milk: Place the dish in a larger pan and add water to the outer pan until it reaches halfway up the sides of the condensed milk dish. Bake for 1 to 1.5 hours, checking every 30 minutes and adding water as necessary.

4. Cool and use: Once the milk has thickened and become golden brown, remove from the oven and cool before using.

Stovetop (Quick Caramelization Method):

1. Combine milk and sugar (optional): In a saucepan, add sweetened condensed milk and ¼ cup of granulated sugar (optional, for extra caramel flavor).

2. Cook over low heat: Stir constantly to prevent burning. Simmer for 20-30 minutes until the mixture thickens and turns golden brown.

3. Cool and store: Once done, cool and transfer to an airtight container for storage.