If you have a large piece of cocoa butter, chop it into smaller pieces. You can have it in uneven chunks, and I'll often do it this way, but the smaller, more even pieces will melt faster and more evenly.
Set up a double boiler by placing a heat-proof bowl over a pan of water. Make sure that the water isn't touching the bottom of the bowl and set over medium-low heat. Bring to a gentle simmer - don't boil as this increases the risk of scorching and water getting into your chocolate which may cause it to seize.
Add the cocoa butter to the bowl to melt without scorching or reaching temperatures that are too high. Stir or whisk* the cocoa butter often during this process to ensure even melting.
Once melted, add the powdered sugar and stir well to dissolve it.
Then add the milk powder and stir to incorporate.
Transfer the melted whited chocolate to a blender/food processor and blend to make the mixture smooth.**Alternatively, if you have a chocolate grinder ( chocolate melanger), you can let it run for several hours to grind the chocolate. This will grind the particles within the chocolate into tiny tiny microparticles until they are no longer discernible by the human tongue - like commercial chocolate.
Pour the mixture into the mould/s of your choice and leave in the fridge or freezer to set. You can then transfer the chocolate to an airtight container in the fridge (or keep it in the freezer).
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Notes
*It's best to use plastic/silicone or whisks for this, rather than wooden spoons, as wood may hold moisture and affect the chocolate. ** If you want to add any additional flavorings then it's usually best to do this once the heat is off. You can also sprinkle 'toppings' directly into your chocolate molds. How To Store:Because of the fact that this homemade white chocolate is untempered, I keep mine stored in the fridge. It will last for 2 weeks in the fridge. Alternatively, keep them stored in the freezer for a few months (if they last that long!).Further Notes & Variations
Some cocoa butter is sold with cosmetic uses in mind and may not be food-safe. Be sure to buy food-safe cocoa butter for this recipe
This white chocolate recipe sets very solid. However, as it is untempered chocolate, it is best stored within the fridge.
If you don't want to blend the chocolate mixture then it's VERY important to sift the dry powders into the melted cacao butter.
To temper the white chocolate, use one of these chocolate tempering methods. Once tempered you can use the chocolate for truffles and bonbons and even store it at room temperature.
Reduce the amount of milk powder used for less "rich" white chocolate.
If, at any point, your chocolate seizes then slowly add a little additional cacao butter or vegetable shortening (1tsp at a time) and it should help bring it back together.