Preheat your oven to 375°F (190°C). Line a 15″×10″ cookie sheet with rims with parchment paper.

Lay a single layer of saltine crackers in the pan, covering the bottom as evenly as possible.

In a small saucepan over medium low heat, place the butter and brown sugar. Stir frequently and bring to a full boil. As soon as it’s boiling, reduce the heat to low and cook for exactly 3 minutes, stirring constantly.

Immediately pour the hot brown sugar–butter mixture evenly over the saltine crackers in the pan. Use a spatula to spread and coat the crackers if necessary.

Transfer the pan to the oven and bake for 5 minutes. The toffee mixture will be very bubbly when you take it out.

Remove from the oven and place the baking sheet on a cooling rack. Immediately sprinkle the chocolate chips over the top of the hot caramel and crackers. Wait a couple of minutes until the chips begin to melt.

Using an offset spatula or butter knife, spread the melted chocolate evenly over the surface.

While the chocolate is still warm, add your optional toppings: sprinkles, mini M&Ms, or a light dusting of flaky sea salt.

Let the toffee cool until completely hard — this may take an hour or more at room temperature. To speed things up, you can place the sheet in the fridge.

Once set, cut into squares and serve.