EMB-145 flight crew reported encountering severe turbulence in descent causing a momentary loss of aircraft control.

Narrative

Leaving ZZZ1 encountered constant moderate turbulence with deviations in airspeed plus or minus 30 on climb out. Once we were about to fly east away from the weather it smoothed out a bit and was OK until we got around ZZZ. When given a descent to 5;000 ft by approach from about 8;000 to 6;000 ft we encountered what I would consider severe turbulence. Autopilot kicked off; put us in a 40 degree bank and heavy fluctuations on airspeed. Got control of the aircraft and around 5;000 ft it smoothed out to light turbulence occasional moderate. We informed ATC of the moderate to severe from 8;000 ft to 6;000 ft. We then briefed that we would give the approach a shot as long as the turbulence levels stayed where they were at and didn't pick back up. We then got vectors back around for the approach. Broke out at minimums and safely landed in ZZZ. Upon landing and parking the aircraft. The ground crew informed me that my taxi light was still on even though the switch was off. I cycled it a few times and was able to get it to finally go off. The FA (Flight Attendant) informed me the lights in the cabin were also flickering. Upon conferring with my FA and FO (First Officer) I deemed it necessary to write up the aircraft for severe turbulence. Was the worst turbulence I've encountered in my years at this company.