Line a 5x5-inch baking dish with parchment paper, leaving extra on the sides so you can lift the peppermint bark out easily.
Chop the semi sweet chocolate and place it in a bowl with half of the oil. Melt the chocolate either in the microwave or use a double boiler.Microwave: Heat in 15-second intervals, stirring after each, until smooth.Double Boiler: Place the bowl over a pot of simmering water and stir until melted.
Spread the melted semi sweet chocolate evenly in the prepared dish. Refrigerate for 10 minutes to help it set.
Chop the white chocolate and melt it with the remaining oil using the same method. Stir in the peppermint extract.
Gently spread the melted white chocolate over the chilled chocolate layer. Sprinkle crushed peppermint candy over the top.
Refrigerate the peppermint bark for 30 minutes, or until fully set.
Lift the bark out using the parchment paper, remove the paper, and break the bark into pieces.
Notes
Melt Chocolate Slowly: Heat chocolate in 15-second intervals and stir well between each. Short bursts prevent scorching and help it melt smoothly.
Go Easy on Peppermint Extract: Use a light hand. Start with the small amount listed and adjust only if needed.
Let the Layers Set: Chill the first chocolate layer until almost firm before adding the next to keep the layers clean and defined.
Use Parchment Paper: Line the dish with parchment and leave extra hanging over the sides so the peppermint bark lifts out easily once set.