Put the chocolate chips in a bowl and place the bowl over a pot of simmering water. Stir until the chips are melted. (Alternately, put the chips in a microwave safe bowl and microwave on medium for 30 seconds. Stir and microwave in 30 second intervals until the chocolate has melted. It should take 2 to 3 minutes.) Add 3 tablespoons of the vegetable oil and stir well.
To form the base, dip two pretzel sticks in the chocolate and lay them side by side on a waxed paper-lined baking sheet. Repeat until you have 24 bases made. Put the baking sheet into the refrigerator to harden the chocolate. Pour the remaining chocolate into a squeeze bottle.
Meanwhile, add the hazelnuts, sugar, and vanilla to the bowl of a food processor. With the machine running, pour in the remaining 2 tablespoons vegetable oil. Continue processing until the nuts form a smooth spread. Scoop the spread into a plastic bag and snip off a corner to make a piping bag. Remove the bases from the refrigerator and pipe a strip of hazelnut spread between each pair of chocolate covered pretzels. Squeeze chocolate over the top of each one to cover and return the baking sheet to the refrigerator for at least 1 hour. Trim off any excess chocolate with a knife and wrap each bar individually. Keep refrigerated.