Warm the coconut oil. Gently melt it in a heat-safe bowl over warm water or in short, low-power bursts in the microwave. You want it liquid, not hot.
Infuse with coffee. Stir in the ground coffee. Let the mixture sit for 20–30 minutes, stirring occasionally.
For a stronger infusion, let it sit up to 2 hours at room temperature.
Strain well. Pour the mixture through a fine strainer, coffee filter, or cheesecloth into your clean jar. Make sure no coffee grounds remain—they can scratch delicate under-eye skin.
Add boosters (optional). Stir in vitamin E oil and a few drops of almond or jojoba oil to make the texture silkier and less greasy.
Let it set. If your home is cool, the serum may firm up. That’s normal for coconut oil. To use, warm a tiny amount between your fingers to liquefy.