Spray a 9x13 glass baking dish with cooking spray. Set aside.

Add the first 4 ingredients (puffed rice through sunflower seeds) to a medium bowl and stir to combine. Set aside.

Melt the butter in a large pot over medium heat. Add the marshmallows and stir to coat with melted butter. When the marshmallows have melted, remove from the heat and pour in the rice and oat mixture. Stir well to combine. Pour in to prepared baking dish and press the mixture firmly using a small piece of waxed paper, parchment paper or the wrapper from the butter. Allow to cool for 30 minutes. Turn out onto a cutting board and cut into 18 bars.

Melt chocolate on top of a double boiler simmering over medium-low heat. When the chocolate has melted completely, remove from the heat and dip the bottom of each bar in the chocolate and place on a piece of parchment paper. Allow chocolate to harden for 30 minutes and then enjoy.