The 35-year-old beauty guru - who recently celebrated 10 years of working with the 'Keeping Up with the Kardashians' star - has revealed that some of his most "iconic looks" with Kim, 37, have happened because the duo "trust" each other and both have a say in what products they are using for her face but liquid concealer is there must-use product.
Speaking to Maria Hatzistefanis on her podcast, The Overnight Success, Mario said: "There is definitely some back and forth in everything we do. For example when we were doing one of our most iconic looks with the blue eyeshadow, Kim starting saying, 'Oh no it's too much!' And I was just like, 'No it's not, just let me finish and you'll see', so she has to trust me and I have to trust her.
"We used to use really light concealer under the eye. It doesn't make me cringe to think back on it though, people loved it and we loved it at the time.
"And although the shade of concealers has changed, the technique has always stayed the same, beginning with liquids, followed by baking before blending and finishing it off."
Mario - who has worked as a makeup artist for all of the Kardashian clan - also revealed that he loves Kim's sister Kylie Jenner's beauty products and he hoards as many as he can.
He said: "I'm the biggest hoarder of Kylie Cosmetics. I literally have boxes and boxes at my house that I'm collecting. They're just so iconic I want to keep them forever. Her black gel eyeliner is so good and is in my kit a lot."