Chemistry was not my greatest subject. Luckily, balancing chemical equations doesn't serve me in my current vocation. (My best subject was—can you guess?—show choir. Flying colors every semester, baby.) But a form of chemistry returned to me a few weeks ago at New York's Heyday, when my facialist Alex and I got to talking products for my very specific skin type.

Actually, it started off as more of an argument. Alex wants me to wear oil on my face to bed, so my skin can binge out on fatty acids all night. But I can't do oils! I don't like the slick feeling. I much prefer something creamier—that kind of masky, filmy vibe on my face for sleeping time. So Alex recommended a happy medium for me: take a nourishing garden variety rosehip oil, and mix it with a basic, creamy product, like Naturopathica's Aloe Gel Mask. I get the texture I want with the ingredients she wants. Success!

Now I'm a mixing fiend. I mix my Priming Moisturizer with my Burberry Fresh Glow for tinted moisturizer. I layer my vetiver fragrance with a sandalwood perfume oil for a beachy take on my signature scent. Last weekend, I made a guerilla cocktail with rosé and sugar-free Red Bull to see how it would taste. Two out of three successes!

Pretend you and I have been plopped right into the middle of a Harry Potter book. This is Potions 101. You're Snape, I'm Hermione, and the topic of the day is: beauty. (And maybe cocktails.) What sorcery are you whipping up with the products in your medicine cabinet? Extra credit for recipes.

—Brennan Kilbane

Photographed by Tom Newton.

Next lesson: DIY your own high-impact mascara. Or answer more burning questions in ITG's Open Thread.