Prepare a cookie sheet with parchment paper and set aside. (if you want a thin toffee then prepare 2 cookie sheets).

In a large heavy bottomed pan, (the heavy bottom helps regulate heat better and prevents scorching more), add butter, sugar, corn syrup and salt and begin cooking until sugar begins to dissolve and the mixture becomes liquidy.

Slowly pour in your cream while stirring at this point.

Bring mixture to a boil and cook until it reaches hard crack stage with your ice water test (see instructions above) or about 305 F. with a candy thermometer, remove from heat and continue stirring hot mixture in the pot for about 2-3 minutes, the mixture will stop boiling during this time.

Pour mixture onto your lined cookie sheets and smooth out with a rubber spatula. You can bang the pan against the counter top to help any bubbles some to the surface then press them out with the rubber spatula.

The toffee will begin setting up immediately, once it has a semi-hard film across the top, sprinkle on your chocolate chips if using them and let them melt.

Once they are melted, use a rubber spatula to smooth the chocolate over the tops.

Optional - Add m&m's, crushed nuts, sea salt or whatever you want on top and let the chocolate and toffee cool completely.

When cooled, lift up toffee block and begin cracking into desired sizes. I sometimes use a rolling pin to break up into smaller pieces but usually you can just lift and drop on a counter top to break.

Toffee will last on the countertop for a long long time, I've never actually had it go bad because it gets eaten.

Enjoy!