Shoot the floor to reveal a hidden Missile Tank. Proceed to boost-jump through the left wall of the shaft, into an unmapped room. Run to the left to charge up your Speed Booster before you reach the step leading into what used to be Big Momma's House, start a booster-charged Spade Jump to fly past the charred remains of the Mother Brain and into the shaft. Next, travel to the corridor outside of the Save Room (save your progress if you would like). Break the block, drop into the hole into a secret room and pick up a Power Bomb Tank. Set off a Power Bomb at the vengeful creature's remains to expose a Super Missile Block. From the elevator, drop down the shaft you previously couldn't wait to get up and out of and enter the chamber where you fought Mother Brain.
