Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.

Arrange saltine crackers in a single layer on the prepared sheet, salt-side up, cutting or overlapping as needed to cover the surface.

Melt the butter in a saucepan over medium heat.

Add the dark brown sugar to the melted butter and stir until the sugar dissolves; do not boil.

Stir in the vanilla extract and mix well.

Pour the butter-sugar mixture evenly over the crackers.

Bake in the preheated oven for about 10 minutes until the sugar is bubbling.

Remove from oven and immediately sprinkle the milk chocolate chips evenly over the hot sugar; let sit 10 minutes to melt.

Spread the melted chocolate into an even layer, allow to cool completely, then remove from parchment and cut into bars or pieces.