In a medium, deep heavy pot combine the milk, sugar and baking soda and salt and vanilla pod.
Cook over medium heat, stirring occasionally, until sugar melts and the mixture is foamy in appearance. Keep a close eye on it, as it can foam up and overflow rather quickly.
Continue to cook, stirring constantly, until it changes to a golden brown and is thick enough to coat the back of a spoon. Be patient, it takes a while for the mixture to reduce and thicken.
Remove from heat and remove the vanilla pod. Allow to cool, then transfer to a piping bag.
Ganache:
Melt the white chocolate in a stainless steel bowl over a pot of simmering water.
Place the chevre, vanilla beans and butter in a stainless steel bowl and cream, using a wooden spoon.
Add the melted white chocolate to the chevre mixture and stir until smooth and fully incorporated.
Allow to cool, then transfer to a piping bag.
Chocolate:
Prepare molds by coating with your choice of cocoa colours in your preferred method. I used a combination of finger painting and airbrushing.
Temper the dark chocolate according to the manufacturer's instruction. Check my post here.
Allow to set, then pipe the cajeta into the molded shell, filling about one-third of the way. Top up with the chevre ganache, leaving enough room at the top to cap. Allow to set, then apply a thing layer of dark chocolate to cap.
Allow to set for about 10-15 minutes, then place in the fridge for an additional 10 minutes.
Unmold the bonbons by inverting the mold and tapping firmly onto a clean, even surface. The bonbons should fall out effortlessly.