Spread the milk solids over a sheet pan lined with parchment paper.
Toast until browned in a 160°C/320°F oven, 7 to 10 minutes; move the milk solids around with an offset spatula every few minutes to ensure even toasting.
Cool to room temperature.
Have 10 silicone ring molds measuring 10cm/4in external diameter by 2.5cm/1in internal diameter by 5mm/.2in deep (see Resources) set on a sheet pan on hand.
Combine the milk solids, heavy cream, and sugar in a small sauce pot and bring to a boil over high heat. Turn off the heat. Use a handheld blender to ensure that the milk solids have dissolved completely into the cream.
Stir in the gelatin and mix until it has dissolved completely. Pour into the silicone ring molds. Set in a freezer.
Once frozen, you can unmold them onto a half sheet pan lined with a nonstick rubber mat. Reserve frozen.
Meanwhile, set up a spray station, a surface that should be covered with plastic to keep the shop clean where you can spray the panna cotta.
Melt the caramelized milk chocolate velvet spray. Fill a compressor canister and spray the panna cotta with an even coating of spray. Keep the compressor gun at least 60cm/24in from the panna cotta to obtain a velvety smooth look. Reserve frozen. If you do not keep them frozen, it will be impossible to transfer them to the serving plate without them losing their shape.