Preheat the oven to 400°F.
Line a 9x13 cookie sheet with aluminum foil or parchment paper. Expert Tip: If using aluminum foil, spray with a non-stick spray. There is no need to grease the parchment paper.
Place saltine crackers side-by-side until the cookie sheet is filled. Set aside.
In a large saucepan, melt the butter and dark brown sugar on medium-high heat.
Bring the mixture to a rolling boil for about 3 minutes while stirring to ensure no sticking or burning.
After the caramel toffee has boiled for about 3 minutes, evenly pour it onto the saltine crackers. Take a spatula and spread the caramel toffee evenly onto the crackers.
Place the cookie sheet into the oven for about 5 minutes, or until the caramel sauce starts to boil.
Remove the cookie sheet from the oven and evenly distribute the semisweet chocolate morsels onto the boiling caramel. NOTE: The chocolate won't be completely melted at this point and that's ok.
Add in the reese's pieces, any other candies, and pecan chips. Take a spatula and spread evenly so the candies can start to melt.
Put the cookie sheet back into the oven and let cook, just long enough for the candies and chocolate to melt, about 5-7 minutes.
Once the chocolate morsels have melted, remove the cookie sheet from the oven and place in the refrigerator for 1-2 hours to chill.
Once the bark has completely cooled and is cold, remove the cookie sheet from the refrigerator and start to break the bark into bite size pieces.
Store the candy bark in the refrigerator or in an airtight container on the counter for up to 2 weeks.