Preparation

This recipe transforms humble egg yolks through enzymatic curing that breaks down proteins and concentrates flavors. The koji provides umami while coffee adds bitter, earthy notes that complement the richness.

Preparing the Curing Medium

1. Spread espresso grounds on a baking sheet and dry in a 200°F oven for 30 minutes, stirring occasionally.
2. Once completely dry, mix grounds with koji, salt, sugar, pepper, and paprika.
3. Divide mixture in half.

Curing the Yolks

1. Spread half the curing mixture in a shallow container.
2. Using the back of a spoon, create 12 evenly spaced indentations.
3. Carefully separate eggs, placing one yolk in each indentation.
4. Gently cover yolks with remaining curing mixture, ensuring they're completely buried.
5. Cover container and refrigerate for 7 days.
6. The yolks will firm up significantly as the salt and enzymes cure them.

Drying and Aging

1. After 7 days, gently brush off the curing mixture from each yolk.
2. Rinse very briefly under cold water and pat dry with paper towels.
3. Place yolks on a wire rack over a baking sheet.
4. Dry in the refrigerator, uncovered, for another 3-7 days.
5. They should become firm and almost waxy in texture.

The finished yolks can be grated with a microplane over pasta, salads, rice bowls, or roasted vegetables. Each yolk provides about 2 tablespoons of intense, funky, umami-rich garnish. Store wrapped in parchment in the refrigerator for up to 2 months.