The most unexpected and unprepossessing ingredients can sometimes take on a new life when they're taken out of their usual context. Ordinary saltine crackers, for example, are typically employed as a blandly neutral complement to a bowl of soup or a smear of peanut butter. If they're used instead as a base for chocolate "bark" candy, the crisp crackers are utterly transformed into a richly alluring dessert.
Preheat your oven to 350 degrees. While it's warming, line a jelly-roll pan or half-sheet pan with parchment paper or non-stick aluminum foil. Ordinary foil will also work, if it's liberally sprayed with cooking oil to prevent sticking.
Arrange saltine crackers to cover the sheet pan in a single layer, without overlapping at the edges. You'll need approximately 40 to 50 crackers, depending on the size of your pan. Snap the crackers in half to fill any awkward spaces near the pan's edges.
Combine butter and brown sugar in a heavy-bottomed saucepan, and bring it to a boil on your stovetop. You can use 2 parts sugar to 1 part butter, by volume, or use equal measures of sugar and butter for a richer flavor. One cup of sugar is adequate for a single pan of bark. Increase your quantities for each additional pan.
Boil the sugar and butter together for 3 to 6 minutes, until mixture's color begins to darken and it thickens slightly. Remove the sugar mixture from your burner and let it sit for a minute or two, then stir in a splash of vanilla extract.
Pour the sugar mixture over your crackers, spreading it evenly with a lightly oiled spatula or the back of a spoon. If any of the crackers shift from their position, slide them back with a wet finger. Bake the crackers for 5 to 10 minutes, until the sugar mixture is brown and bubbly and smells of butterscotch.
Remove your sheet pan from the oven and scatter chocolate chips over the hot surface of the butterscotch. You'll need roughly 1 1/2 cups of chips for each pan of bark.
Spread the melted chocolate evenly across the top of the butterscotch mixture, then let it cool. Refrigerate your sheet of bark until it's hard, then break the slab of candy into serving-sized pieces.