This doesn't work. To start with, you can't cast a bonus action spell and another leveled spell in the same turn.
A spell cast with a bonus action is especially swift. You
must use a bonus action on your turn to cast the spell,
provided that you haven’t already taken a bonus action
this turn. You can’t cast another spell during the same
turn, except for a cantrip with a casting time of 1 action.
Secondly, the Fog Cloud spell makes an area heavily obscured.
A heavily obscured area—such as darkness, opaque
fog, or dense foliage—blocks vision entirely. A creature
effectively suffers from the blinded condition (see
appendix A) when trying to see something in that area.
In case the blinded condition needs explaining,:
A blinded creature can’t see and automatically fails any
ability check that requires sight.
Misty Step lets you teleport to somewhere you can see - you can't see anything if you're in a Fog Cloud, so you can't use Misty Step at all.
Thirdly, it doesn't matter whether enemies can see where you teleport from. You want to hide the location you're teleporting to, so this is all pointless anyway.