Warm the base: In a small saucepan over low heat, combine milk, butter, and corn syrup. Stir until the butter melts and the mixture is warm but not simmering. Remove from heat and stir in vanilla.

Bloom the cocoa: Whisk in the cocoa powder until smooth. This “blooms” the cocoa, deepening the flavor and giving you a glossy base.

Melt the chocolate: Add the chopped semisweet chocolate to the warm mixture. Let it sit for 1 minute, then whisk until completely melted and silky.

Sweeten and thicken: Sift the confectioners’ sugar over the pan. Whisk gently until no lumps remain. Add a pinch of salt to balance the sweetness.

Adjust consistency: You’re aiming for a thick, pourable glaze that ribbons off a spoon and smooths out within 5–7 seconds. If too thick, add 1–2 teaspoons warm milk. If too thin, whisk in an extra tablespoon or two of sifted confectioners’ sugar.

Dip the donuts: Transfer the glaze to a shallow bowl. Dip the top of each donut, letting excess drip back into the bowl. Flip right-side up and give a little twist as you pull away for a clean edge.

Set on a rack: Place glazed donuts on a wire rack set over a sheet pan. Let them sit at room temperature. The glaze will set in 15–25 minutes, depending on your kitchen’s temperature and humidity.

Optional finish: Add sprinkles, chopped nuts, or flaky salt right after dipping, while the glaze is still tacky.