Whisk the dry base: In a small bowl, whisk 1/2 cup unsweetened cocoa powder with 3/4 cup granulated sugar and a pinch (1/8 teaspoon) of fine salt. This helps the cocoa disperse evenly and prevents lumps.

Bloom with liquid: In a medium saucepan off the heat, add 1/3 cup water (or coffee). Sprinkle in the cocoa-sugar mixture while whisking to form a thick paste. This “blooming” step releases deeper chocolate flavor.

Add cream and syrup: Whisk in 3/4 cup heavy cream and 1 tablespoon light corn syrup or honey. The syrup is optional but highly recommended for shine and a smoother texture.

Gently heat: Set the pan over medium-low heat. Cook, whisking often, until the mixture is steaming and just starting to bubble around the edges. Do not let it rapidly boil. This takes about 3–5 minutes.

Smooth and finish: Remove from heat. Whisk in 2 tablespoons unsalted butter until fully melted and glossy, then stir in 1 teaspoon vanilla extract. Taste. If you want more intensity, add a tiny pinch of espresso powder.

Adjust thickness: For a thinner sauce, whisk in 1–2 tablespoons warm water or cream until it flows how you like. For a thicker, hot-fudge style sauce, return to low heat for 1–2 minutes, stirring, until slightly reduced.

Serve warm: Pour over ice cream, spoon onto cake slices, or swirl into milkshakes. The sauce will thicken as it cools, so use while warm for the best drizzle.