Back in 1991 there was an accident off the coast of East Sale with a RAAF 707 from 33 SQN Richmond getting itself into a VMCA loss of control scenario at too low an altitude to recover resulting in loss of five lives.
VMCA1 or VMCA2 is a term that comes from the French, and refers to the minimum speed for control, with one or two engines out (on the same side), with take off power set. VMCA2 for the A380 is 144 knots, which is an impressively low speed given the power and moment arm of the engines.
What it means is that if you have asymmetric power (because of an engine shutdown, or demonstration) there is a speed below which the rudder will not have sufficient authority to keep the aircraft straight, so it will start to yaw and roll. During the take off roll, that speed is an abort consideration, as you cannot continue after an engine failure if you don’t have enough to rudder to keep the aircraft straight. It’s VMCG on the ground.
It’s dealt with in the sims, but can be reasonably safely looked at in flight (and test flights have to demonstrate that calculated VMCs are correct).
So, to do it safely in flight...firstly have a reasonable altitude, but it doesn’t have to be in the stratosphere. In the configuration that you’re going to use, slow the aircraft to about 220 or so knots, but well above VMCA. Gently (!) set up the power configuration you want (say two engines at idle, and the other two at MCT). The aircraft will almost certainly start to accelerate, so gently pitch the nose up until you get a gentle deceleration. As it slows you’ll need more and more rudder, until eventually you’ll hit the rudder stops. From that point you won’t be able to stop the roll and yaw, but it will fairly gently roll. At that point the only way to regain control is to balance up the power again, and taking them all back to idle, lowering the nose, and then gently introducing the power again will achieve that.
What you do not do is set the event up by slowing to well below VMCA, and then suddenly introducing the full amount of asymmetric power. In that case the departure will be rapid and violent.
At about the time that this event happened, the RAAF was suffering from a marked loss of its mid level experience and oversight, with airline recruitment having an effect across the board.