He's already revealed some of his secret on Spoiled Pretty.com.
FULL coverage concealer (cream) applied with a blending brush + Blend with a damp sponge + Translucent powder on top with the same sponge. Brush off the excess powder.
Mario D sometimes uses a lighter shade loose powder to set the concealer. When the flash goes off, the undereye area appears much brighter.
TIP: Using a little brightening powder like Laura Mercier Secret Brightening or Benefit Powderflage will help diffuse light and hide dark cicles under the eyes.
Hope that helps!
PS: Another trick Mario does is, he will use a powder bronzer around the hairline and hollows of the cheeks. This contouring technique makes the highlighted concealer to appear more obvious.
