Line a 9x13 baking dish with foil and spray generously with non stick cooking spray.

In a large cooking pot, melt butter gently over low flame.

Once butter has melted, stir in 16 cups of mini marshmallows.

Continue stirring marshmallows and butter over low heat until marshmallows have melted.

Remove marshmallow mixture from heat and stir in Fruity Pebbles cereal and salt.

Stir gently to combine.

Stir in additional 4 cups of marshmallows reserving a handful to press on top of the bars.

Transfer to baking dish, then top with remaining marshmallows.

Use slightly damp hands to gently flatten.

Let cool 30 minutes and cut into bars.