I'm not sure about "light & fluffy" peanut brittle but this is quickest, easiest, best recipe I've used to make peanut brittle.

PEANUT BRITTLE

Microwave following ingredients for 4 minutes on high. Stir, cook 4-1/2 more minutes.

1 cup sugar
1/2 cup white Karo
1 cup unsalted peanuts

Then add following and cook 1-1/2 minutes:

1 tsp vanilla
1 tbls. butter

Mix in

1 tsp baking soda

Pour onto greased cookie sheet and let cool. Break up into pieces.