Arrange the two jokers and blank card so the mirror joker is face up behind the blank card (with the blank side facing up), with the normal joker on top, also face up.
Place the stack of three cards face down on top of the deck of cards, so the mirror joker is now on top of the deck, followed by the blank card and the normal joker.
Flip over the top two cards---the mirror joker and the blank card---fast enough so it seems as if only one card (the blank card) was flipped, with its blank side facing out.
Flip over the normal joker card to show its face to the audience. As you do this, slide the joker forward on the deck just a bit.
Lay the mirror joker and blank card face down on top of the normal joker's face.
Slide the top card---the mirror joker---forward, and pull the two jokers off the deck at once, leaving the blank card behind by keeping a thumb on it. The key is to perform Step 5 and this step as fluidly as possible, so the audience does not notice the blank card being slid out from between the two jokers.
Pull the two jokers apart like two pages stuck together with wet ink. To the audience it looks as though the inverted image of the normal joker has been printed onto the blank card.