Line a baking sheet with foil and butter the foil. Set one cup of potato chips aside; break the remaining 4 cups of chips in half if they are large.
Combine the butter, sugar, vanilla and vinegar in a sauce pan over medium-high heat and cook, stirring occasionally, until the mixture is light amber and a candy thermometer reads 320 degrees, about 10 minutes. Remove from the heat and stir in the 4 cups of chips, then immediately pour onto the baking sheet and spread in a thin layer. Gently press the reserved one cup chips on top and let cool.
Put about 3/4 of the chocolate in a microwave safe glass bowl and microwave for 30 seconds. Stir, then continue to microwave 30 second intervals, stirring between each, until melted. Add the remaining chocolate and stir until smooth, about 4 minutes.
Drizzle the chocolate over the toffee. Set aside to harden, about 20 minutes. Break the toffee into pieces.