Combine both chips and brown sugar in a heatproof bowl (preferably with a spout), and set aside.
Combine both milks in a small saucepan and heat over medium-low heat, whisking frequently. (The faster you whisk, the foamier the milk will be.)
When the milk looks like it's about to boil, remove from heat and pour into bowl over the chips and sugar.
Let sit about 1 minute, then whisk until completely smooth.
Pour into a mug and enjoy!