Hot chocolate bombs with tempered chocolate shells and homemade cocoa mix

Bring about an inch of water to a simmer over medium heat. Chop the chocolate and put it in a bowl that sits on top.

Melt over the simmering water, stirring, without letting it go above 90 degrees; check with a digital thermometer. In a microwave, use 15-second half-power bursts.

If it overheats (it reached almost 110), seed it: stir in one third of its weight in extra chocolate until it cools to 82 degrees.

Test: swipe a little on parchment and refrigerate about two minutes; shiny and crisp means it is tempered.

If not, rewarm into the low 90s and seed again with 50 g of chocolate, mixing until melted.

Spoon chocolate into each hemisphere and work it up the sides, removing the excess; go back over the edges so the top is thin but not too thin, and patch any thin spots.

Whisk the cocoa powder, granulated sugar and a pinch of salt into a hot chocolate mix.

Warm a pan (warm, not hot) on a trivet; unmold a dome and set it rim-down on the pan to melt the edge smooth.

Fill each half with about two tablespoons of the mix and a mound of mini marshmallows, keeping them off the edge; melt the edge of a second half and press on to seal. Wipe away excess with a knife.

Drizzle or pipe white chocolate or candy melts over the top and add sprinkles.

Put a bomb in a big cup and pour very hot milk over it; stir.