How to Make It
Preheat the oven to 350°. Put the ice cream in the refrigerator until just softened, about 15 minutes. Line a baking sheet with wax paper and transfer it to the freezer.
Meanwhile, spread the pecans on a baking sheet and toast until fragrant and browned, 8 minutes; transfer to a food processor and let cool completely. Coarsely chop the nuts and transfer to a pie plate.
Using a standard ice cream scoop, scoop a 1/2-cup portion of ice cream onto the pecans and roll into a ball, pressing lightly to help the nuts adhere. Transfer the ice cream ball to the prepared baking sheet in the freezer. Repeat with the remaining ice cream and pecans. Freeze the ice cream balls for at least 3 hours before serving.
Meanwhile, in a medium saucepan, combine the chocolate chips, condensed milk and butter and cook over low heat, stirring, until the chips are completely melted and the sauce is smooth. Remove from the heat and stir in the vanilla. Transfer the sauce to a pitcher.
Serve the ice cream in bowls or sundae cups and drizzle with the warm sauce.