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. Place 2 sleeves of saltine crackers side-by-side until the baking sheet is filled. Set aside.
In a large saucepan, melt 1 cup of butter and 1 cup of 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 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. Do this quickly because the toffee will start to harden.
Place the cookie sheet into the oven for about 5 minutes, or until the toffee starts to boil.
Remove the baking sheet from the oven and evenly distribute 12 ounces of semisweet chocolate morsels onto the boiling caramel. NOTE: The chocolate won't be completely melted at this point and that's ok. Add in ½ cup Reese's pieces, any other candies, and pecan chips. Take a spatula and spread evenly so the candies can start to melt.
Put the baking 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 baking sheet from the oven and place in the refrigerator for 2 hours to chill.
Once it has completely cooled and is cold, remove the baking sheet from the refrigerator and start to break the crack candy into bite size pieces.
Store in the refrigerator or in an airtight container on the counter for up to 2 weeks.