01 -
Butter a 9-inch square baking pan. For easier removal, line it with parchment and butter the parchment lightly.
02 -
Set a heatproof bowl over a saucepan of gently simmering water. Add the chocolate chips, butterscotch chips, and sweetened condensed milk. Stir until melted, smooth, and glossy, about 4-5 minutes.
03 -
Remove the bowl from the heat. Stir in the vanilla and chopped pecans until evenly mixed.
04 -
Scrape the fudge into the prepared pan. Smooth the top quickly with a buttered spatula because the mixture thickens as it cools.
05 -
Refrigerate until firm, at least 30 minutes. Lift from the pan if using parchment, then cut into small squares.