Preheat the oven to 250°F (120°C). Chop up pieces of white chocolate until they look splintered. You want the surface area of the chocolate slivers to be as small as possible so that each one is evenly exposed to the heat.
Scrape your chopped chocolate on a baking sheet. Spread out the chocolates in a single layer to ensure even browning.
Put the chocolate-covered tray in the oven and set the timer for 10 minutes. When the timer goes off, take out the baking sheet and use your spatula to stir and move the melted chocolate before returning it to the oven for another 10 minutes.
Repeat this process two more times (total of 30 minutes) and then every 5 minutes afterward until the chocolate is smooth and deep brown. It should be roughly the color of peanut butter, according to my boss in Guatemala (where I learned this technique many years ago).
Once it’s out of the oven, let it cool first. If the chocolate is separated or is a bit grainy, scrape it into a high-speed blender (you can also use an immersion blender or a food processor) and recombine for a smoother texture.
You can use it immediately for recipes that call for melted chocolate, or you can transfer it to an airtight container for later use. This can be stored for up to a month, no refrigeration required.