Step 1: Caramelizing the Sugar

1. Place a heavy-bottomed saucepan over medium-low heat.
2. Add the brown sugar, spreading it evenly across the pan.
3. Allow the sugar to melt gradually without stirring. As the edges start to liquefy, begin stirring with a heat-resistant spatula.
4. Continue stirring as the sugar turns a deep amber color. Be careful not to let it burn, as this can cause bitterness.

Step 2: Adding Liquid Ingredients

1. Slowly pour in the warm water, stirring continuously to prevent sugar crystallization. Expect some bubbling as the liquid meets the hot caramel.
2. Stir in the molasses, ensuring it fully dissolves.
3. If using, add the vinegar, salt, and soy sauce (or Worcestershire sauce), mixing well to incorporate all flavors.

Step 3: Simmering and Adjusting Consistency

1. Lower the heat and let the sauce simmer for 2-3 minutes, allowing the flavors to meld.
2. If the sauce is too thick, add a small amount of warm water until it reaches your preferred consistency.
3. If the flavor is too bitter, balance it with a pinch of sugar.
4. Taste and adjust the seasonings as needed.

Step 4: Cooling and Storage

1. Remove from heat and let the sauce cool completely.
2. Transfer to a sterilized glass jar or an airtight container.
3. Store in the refrigerator for up to 1 month. For longer storage, divide into small portions and freeze for up to 3 months.