Pre-heat oven to 175 degrees Celsius and grease a square 23cm non stick baking pan (if using a regular pan line with foil then grease).
Melt the butter on a low heat (or low power in the microwave). Remove from heat and add to a large mixing bowl, with sugar. Beat butter and sugar until smooth.
Add egg and vanilla, continue beating until completely combined.
Add salt and slowly mix in the flour until smooth.
Roughly quarter each fun size snickers and stir into mixture. Break chocolate into squares and stir into mixture.
Using a spatula transfer mixture into prepared baking pan making sure the mix is evenly spread. Bake for 20-25 minutes.