Creamy, briny, and filled with sperm, shirako is the sort of seafood delicacy that some folks prefer to savor before they learn of its provenance. But dishes featuring these sperm sacs of fish, also known as milt, sell for a pretty penny when they’re in season in Japan.

Milt can actually come from any sea creature that sprays its seminal seed, including most fish, mollusks, and cephalopods. Although the viscous fluid can be mixed with other ingredients, most cooks elect to leave the sac intact, preserving shirako’s light, fine texture, which some liken to brains. To avoid a tough outer sack and granular inner texture, the milt should be cooked just until the outside begins to tighten while the inside remains like a thick, melty cream cheese.

The genitalia can be steamed to best capture their sweetness, dipped in tempura batter and fried to produce a crunchy-coated custard, or served raw atop gunkan maki sushi. Several types of shirako find their way into prized dishes, including as a subtly-sweet floating garnish on chawanmushi, a Japanese-style egg custard.