Butter an 8×8 baking dish or line foil that has been greased with butter.

Melt butter in a large glass bowl in microwave. (Personally, I prefer to do this part on the stove top). Mix in the light corn syrup. sugar, brown sugar, and sweetened condensed milk until combined.

Microwave for 6 minutes. All microwaves are different so you may need longer. Use hot pads to remove from microwave. Add some ice cubes to a glass of cold water. Drop a small spoonful of caramel into the ice water and test the consistency. Does it form a soft ball. If not, allow it to cook 30 seconds longer.

Add vanilla and stir until combined.

Carefully pour caramel into prepared baking dish. Allow to fully cool before you cut them. Caramels do not require refrigeration. However, once they are cool enough, I like to place them in the refrigerator to cool the rest of the way and cut. I think they cut easier. I also remove them from the pan with the foil to cut. Just make sure no foil stuck to the caramels.