In a medium-sized heat-safe bowl, place the cacao butter and shortening.
Heat indirectly by placing the bowl over small pot of simmering water, making sure that the bowl doesn’t touch the water.
Allow the cacao butter and shortening to melt, stirring occasionally. The mixture will be thin.
With the mixture still over the simmering water, add the nut butter and mix to combine.
Add the confectioner’s sugar, salt and vanilla, and mix until smooth.
Remove the bowl from the pot and allow to cool briefly before transferring the mixture to a measuring cup for pouring into molds.
Pour the mixture into silicone molds (really any flexible container will do) and refrigerate (or leave at room temperature) for about 30 minutes, or until solid.
Remove from the molds and serve.
Notes
About the shortening.I like to use Spectrum brand nonhydrogenated vegetable shortening. Crisco works, too.If you'd prefer to eliminate the shortening entirely, you can replace it with an equal amount, by weight, of cacao butter. The resulting white chocolate is much richer.