FOR THE CRUST:
PREHEAT OVEN TO 350F DEGREES. IN A FOOD PROCESSOR, PULSE TOGETHER THE GRAHAM CRACKERS AND BUTTER UNTIL THOROUGHLY COMBINED (IT SHOULD BE THE TEXTURE OF WET SAND.)
PRESS THE CRUMB MIXTURE INTO THE BOTTOM OF A 11 X 7 BAKING PAN. NOTE: IF YOU DON’T HAVE AN 11″ X 7″ BAKING PAN, YOU CAN USE A 9″ X 9″ SQUARE BAKING DISH, THE BARS WILL JUST BE A LITTLE THICKER.
BAKE THE CRUST FOR ABOUT 10 MINUTES, UNTIL GOLDEN BROWN. LET COOL AND LEAVE OVEN ON.
FOR THE FILLING:
MIX EGG YOLKS AND LEMON ZEST WITH AN ELECTRIC MIXER UNTIL VERY THICK, ABOUT 5 MINUTES.
SLOWLY ADD SWEETENED CONDENSED MILK IN A SLOW, STEADY STREAM, MIXING CONSTANTLY.
ADD FRESH LEMON JUICE AND MIX UNTIL COMBINED. SPREAD FILLING EVENLY OVER CRUST AND BAKE AT 350F DEGREES UNTIL FILLING IS JUST SET (ABOUT 12- 15 MINUTES.)
LET COOL COMPLETELY – THEN COVER AND REFRIGERATE FOR A MINIMUM OF 4 HOURS.
FOR THE TOPPING:
BEAT THE COLD HEAVY CREAM WITH POWDERED SUGAR UNTIL FLUFFY.
SPREAD TOPPING EVENLY OVER THE LEMON BARS. DECORATE WITH LEMON ZEST, SLICES OF LEMON ETC. KEEP BARS REFRIGERATED.