In a large saucepan, combine the granulated sugar, brown sugar, and cornstarch together. Whisk until blended, breaking down any clumps of sugar. Turn on the heat to medium. Add in the corn syrup, butter, salt, and eggs and whisk constantly and vigorously to incorporate the eggs to prevent scrambling them. Whisk constantly for about 5-8 minutes or until the mixture starts to boil. Remove from the heat and stir in the pecans and vanilla extract.

Cool the mixture to room temperature completely, then refrigerate to chill for 2 hours or until thickened.

Spoon some of the filling into a large disposable piping bag without an icing tip. Cut the tip of the bag off high enough so that the hole is big enough to accommodate pecans passing through. Pipe the pecan pie filling into one side of the cannoli, pushing the filling into the cannoli to fill it. Fill in any gaps on the other side of the cannoli, if needed. Place the cannoli on a plate or rimmed baking sheet and repeat with remaining cannoli.

Refrigerate the cannoli for about 30 minutes -1 hour or until firm and set. Drizzle with melted candy melts, if using and desired, and let chill for about 10 minutes before serving. Store cannoli in the fridge immediately before serving.