What the White Ingredients Were in Chris Kimball's Cacio E Pepe Telecast

Hi all,

I became intrigued with this recipe after watching the above caption telecast where Christopher prepares the dish with only grated cheese, water, toasted black pepper and artisanal spaghetti/bucatini.

While these are the only ingredients mentioned, I noticed that early on in his preparation he had two small glass mis-en-place bowls next to the cooktop, each with a small amount of white powder both of which he added after pasta and water were heating in the skillet. Salt? flour? corn starch? anyone know what they were and if so, how much of each was added.

Many thanks to whoever can tell me what and how much!

Best,

Richard