In a small mixing bowl, combine flour, baking soda, and salt. Set aside.
Combine brown sugar, white sugar, butter, margarine, and vanilla in a large bowl until well-blended. Add in eggs and beat well.
Slowly add in flour mixture and mix until combined. Add in chocolate and white chocolate chips and then mix the toffee bits until they're just combined.
Drop dough (I use a cookie scoop) onto the cookie sheets and bake 8-10 minutes (10 is perfect in my oven, but each one is different) until the cookies are lightly brown around the edges, even if they don't look like they're done on top.
Allow to cool on cookie sheets for about 5 minutes and then transfer to a cooling rack and cool completely. The cooling rack is very important in this recipe because the toffee will make the cookies stick to the pan if you're not careful.
Notes
If desired, you can use all butter instead of the butter/margarine combination; all butter has a richer flavor, but a little bit of margarine gives these cookies an incredible texture and tends to make this dough easier to work with.
Store cooled cookies in an airtight container and enjoy within 2-3 days for best results.
Feel free to sprinkle a little flaky sea salt on these cookies right after they come out of the oven!