Prepare a baking pan or any rimmed tray by lining it with parchment paper, which makes it easy to lift the white chocolate out after it's set. I used a 9-inch square baking pan for a thick bark, you can use a bigger tray for a thinner bark.
Make a double boiler by placing a pan of water on the stove. Bring it to a boil, lower the heat to a simmer, and then place a heatproof bowl over the pan of water. The bowl should not touch the water or the heat directly.
Add the cocoa butter to the bowl along with the coconut oil. Let them melt completely.
Whisk in the cashew butter and then the sugar. Add the vanilla and mix everything until smooth. You can remove the bowl once everything is mixed. At this point, if you want to, you can use a handheld mixer to whisk the chocolate mixture until very smooth.
Stir in the walnuts, leaving a few to scatter over the top, if you wish.
While the cocoa butter is melting, heat the raspberry in a small skillet to loosen it up a bit, which will make it easier to disperse through the chcoolate.
Pour the white chocolate mixture into the parchment-lined pan and make sure the walnuts are evenly distributed. Drizzle in the raspberry jam, using a skewer or the back of a spoon to ensure it is evenly distributed in uneven, squiggly patterns.
Let the chocolate cool completely, which could take anywhere from 30 minutes to two hours depending on whether you freeze it, refrigerate it, or let it stand in a cool room. I advise refrigerating which should take about two hours.
Once the chocolate is firm and set, remove from the tray, peel off the parchment, and break with your hand into 24 pieces. If it is not yet firm, return it to the fridge and wait until it is.If you want to make it into candy bars, cut with a knife into any size you want.