Melt Butter and Brown Sugar:
In a medium saucepan, melt the butter over low heat. Add the brown sugar and stir constantly until the sugar is completely dissolved. Keep the heat low to avoid burning.

Add Milk:
Once the sugar is dissolved, slowly add the milk to the saucepan, stirring continuously. Increase the heat to medium and bring the mixture to a gentle boil.

Boil:
Allow the mixture to boil for 2-3 minutes, stirring constantly to thicken the frosting.

Cool Mixture:
Remove the saucepan from the heat and let the caramel mixture cool slightly for a few minutes. It should be warm but not too hot when you add the powdered sugar.

Add Powdered Sugar:
Gradually add 2 cups of powdered sugar, mixing well after each addition. Continue to add more powdered sugar as needed to achieve the desired thickness and spreadability. You can use a whisk or an electric mixer for a smoother consistency.

Add Vanilla (Optional):
Stir in the vanilla extract for extra flavor.

Use Immediately:
Once the frosting reaches the right consistency, use it immediately to frost your cake or cupcakes. The frosting will thicken as it cools.