Combine the chocolate chips and butter in the top of a double boiler over simmering, not boiling, water. Stir constantly until the chocolate is melted and combined with the butter. When melted, stir in the oil. Remove the pan from the heat and carefully remove the top of the double boiler. Let cool to room temperature. Pour over ice cream. The sauce will harden on contact. Store the sauce at room temperature for up to one week. Remix if needed before serving.