Add the brandy and craisins to a bowl together, and let them soak for a few hours before you begin preparing the biscotti. This is optional, but adds a depth of flavor from the brandy.
Preheat the oven to 350°F (180°C). Brown the butter by placing it in a small saucepan over medium heat. When it smells nutty and is a light brown color, you're there! Cool it slightly then add to the bowl of a stand mixer with the sugar. Beat on medium until well combined, then add the zest, eggs, and vanilla extract. Beat on medium for 2 minutes until well combined.
In a separate bowl, whisk together the flour and baking powder. Lower the speed on the stand mixer to the lowest setting and add the flour mixture. Stir until no dry pockets remain, then add the craisins (drain off any remaining brandy first if you used it). When they are well incorporated, turn off the stand mixer.
Prepare a baking sheet with a sheet of parchment paper. Pour the dough onto the parchment paper and shape roughly into a rectangle. The most important thing is making sure your dough isn't TOO flat, or uneven around the sides, so that your end product will be roughly the same size. Bake for 25-30 minutes, until golden on top and not raw in the middle.
Cool for about 30 minutes, then cut the biscotti into batons. You should be able to get somewhere between 10-15 out of this dough depending on how you shaped it. Turn the batons on their sides and bake for a further 15-20 minutes, until dry and hard to the touch. Be careful not to burn them!
When you're ready to finish them off, melt the white chocolate with the canola oil in the microwave in 30 second bursts until smooth (stirring between bursts). Dip an end of each biscotti in the white chocolate and allow to harden on a baking sheet. Package them up to give as gifts, or save them for yourself to enjoy with a morning cuppa!