Preheat the oven to 350°F. Line a 15-in. x 10-in. x 1-in. baking pan with heavy-duty foil overlapping the edge. Spray lightly with nonstick cooking spray.
Spread the pecans on a separate baking sheet in a single layer. Toast in the oven for 6-8 minutes until fragrant. Set aside to cool.
Arrange saltines in a single layer on the prepared pan, side by side in a single layer. Set aside.
Meanwhile ,in a large heavy bottomed pot or saucepan over medium heat, melt together the butter and brown sugar. Bring to a boil; cook for 2 minutes stirring constantly or until the sugar has dissolved.
Remove the pot from heat and stir in the vanilla extract. Stir well then pour evenly over crackers. (Be careful, it's hot!)
Transfer to the oven and bake for 5-7 minutes or until bubbly.
Remove from the oven and immediately sprinkle evenly with chocolate chips. Allow the chips to soften for a few minutes, then use an offset spatula to spread over the top from end to end. Sprinkle with toasted pecans and toffee bits.
Chill for 1 hour or until set. Break or cut into desired size pieces.
Store in an airtight container at room temperature or chilled for up to 1 week.