Line your 8-inch square pan with parchment paper, leaving some overhang for easy removal.
Combine butter and sugar in a heavy-bottomed saucepan over medium heat; stir until the mixture begins to bubble and the sugar dissolves, filling your kitchen with a warm, caramel aroma.
Add the cocoa powder to the saucepan and whisk until fully incorporated, creating a dark, glossy mixture that thickens slightly.
Pour in the sweetened condensed milk, stirring constantly to combine everything into a smooth, shiny batter that pulls away from the sides of the pan as it thickens.
Reduce the heat to low and cook, stirring constantly, for about 8-10 minutes until the mixture becomes thick and deep chocolate in color, and you can see it pulling away from the sides of the pan.
Remove from heat and stir in the vanilla extract and a pinch of sea salt, blending until fragrant and well combined.
Pour the hot fudge mixture into your prepared pan, smoothing the top with a spatula for an even surface.
Optional: sprinkle nuts, dried fruits, or sea salt flakes on top for added texture and flavor.
Let the fudge cool at room temperature for at least 2 hours, or until it’s firm enough to cut into squares.
Once cooled and set, lift the fudge out of the pan using the parchment overhang and cut into squares with a sharp knife.
Enjoy your rich, velvety fantasy fudge—perfect for quiet afternoons or sharing with loved ones!
