Preheat your oven to 350°F (175°C). Line a rimmed baking sheet with parchment paper or aluminum foil for easy cleanup.
Arrange graham crackers in a single layer on the prepared baking sheet, covering the entire surface. Break crackers as needed to fill the pan.
Make the toffee layer: In a small saucepan over medium heat, melt the butter and brown sugar together, stirring constantly. Once it begins to bubble, allow it to simmer for 2–3 minutes. Remove from heat and stir in the vanilla extract and a pinch of salt.
Pour the toffee mixture evenly over the graham crackers and spread it with a spatula to fully coat the crackers.
Bake the graham crackers with the toffee layer for 5–7 minutes, or until the toffee is bubbling.
Remove from oven and immediately sprinkle the chocolate chips over the hot toffee. Let sit for 2–3 minutes until softened, then use a spatula to spread the melted chocolate into an even layer.
Add toppings of your choice (such as chopped nuts, sprinkles, crushed candy canes, or flaky sea salt) while the chocolate is still warm.
Chill the pan in the refrigerator for 1–2 hours, or until the chocolate is fully set.
Break into pieces once chilled and firm. Store in an airtight container at room temperature or in the fridge.