In a medium mixing bowl, stir together strawberry drink mix and powdered milk. Set aside.
Add 1 to 2 inches of water to a double boiler and place over medium heat. once simmering and the top pan is warm, add white chocolate and melt until smooth. (see note)
Spoon melted chocolate into molds. Coat the entire mold cavity using the back of the spoon. Place in the fridge until chocolate has hardened, about 15 minutes.
Remove molds from the fridge and carefully remove chocolate half spheres (cups) from the molds. You'll want to press on the bottom so they lift up.
Heat a plate in the microwave for 30 seconds of place the lid onto your double boiler. Press the edges of each chocolate cup onto the warm surface to smooth out the edges.
Fill half of the chocolate cups with 1/4 cup strawberry milk mix, some freeze-dried strawberries, and mini marshmallows.
Take an unfilled chocolate cup and warm the edges again. Press the edges of the filled and unfill cups together to make a sphere. Make sure there are no gaps and smooth any excess chocolate with your fingertip. Repeat with remaining chocolate cups.
Decorate the hot chocolate bombs by drizzling some melted chocolate over the top, sprinkling with crushed freeze-dried strawberries, and adding white chocolate shavings or sprinkles. Store in the fridge until ready to serve.
To serve: Place a hot chocolate bomb into a mug and fill it with hot milk. Stir to dissolve the strawberry milk mix.
Notes
If you don't have a double boiler, you can place a metal or glass mixing bowl over a pot of simmering water instead. Just be sure the bowl is above the water line.