In a medium bowl, microwave chocolate and vegetable oil for about 1 minute. Stir every 20 seconds until smooth.
Place ice cream cones on a small lined baking sheet. (Make sure you have cleared space in your freezer for the sheet.). Drizzle about 1 teaspoon melted chocolate into the bottom of each ice cream cone. Place in the freezer for 10 minutes, to set chocolate.
Remove vanilla ice cream from freezer to let thaw a few minutes before filling cones. Scoop ice cream into cones. Place filled cones into short glasses and onto baking sheet. Freeze for 10 minutes to set ice cream.
One at a time, dip tops of cones in melted chocolate mixture (you may need to warm in your microwave for 15-20 more seconds to thin slightly).
Immediately roll into chopped nuts. If necessary, sprinkle nuts over top to coat evenly.
Place the cones back into the short glasses, onto the baking sheet, and into your freezer.
Repeat process until all sugar cones are filled, dipped and sprinkled with nuts.