Preheat your oven to 400°F (200°C).
Line your baking sheet with parchment paper.
Lay out the saltine crackers in a single layer on the baking sheet.
In a medium saucepan, melt the butter over medium heat. Add the brown sugar and stir continuously until boiling. Boil for 3-4 minutes without stirring, then remove from heat and stir in the vanilla extract.
Pour the hot toffee mixture over the arranged saltine crackers, spreading it evenly with a spatula.
Bake for 5-7 minutes, until bubbly and golden brown.
Remove from the oven and sprinkle chocolate chips over the hot toffee. Allow to sit for a few minutes, then spread the melted chocolate evenly.
If using optional toppings, sprinkle them over the chocolate layer while warm and press down gently.
Cool completely at room temperature, then break into pieces.