Preheat your Oven to 325°F. Grease a 9-inch springform pan with ½ cup unsalted butter cut into pieces, plus extra for greasing and line the bottom with a round of Parchment Paper. Grease the Parchment Paper as well.

Melt the chopped 8 oz bittersweet chocolate 60–70% cacao, roughly chopped and ½ cup unsalted butter cut into pieces, plus extra for greasing together using a Double Boiler over simmering water, stirring frequently until completely smooth. Remove from heat and let cool for 5 minutes. Stir in the 1 tsp instant espresso powder enhances chocolate flavor (if using) and 1 tsp pure vanilla extract.

Whisk the ¾ cup granulated sugar into the warm 8 oz bittersweet chocolate 60–70% cacao, roughly chopped mixture until combined. Add the 4 large eggs room temperature one at a time, whisking well after each addition. The batter will become glossy and slightly thickened.

Crack 2–3 large eggs per serving into a Mixing Bowl. Add a pinch of salt and a few grinds of black pepper. Whisk until fully combined — no white streaks. Optional: add 1–2 tbsp milk (richer) or water (lighter) per serving. Use a nonstick or well-seasoned carbon steel pan. Have a Rubber Spatula or Wooden Spoon ready before the pan goes on heat.

Add ½ tbsp unsalted butter to a Skillet. For creamy curds, use medium-low or low heat. For firmer eggs in less time, use medium — no higher. Once butter melts and coats the pan, pour in your whisked eggs. Let sit undisturbed 20–30 seconds until edges just begin to set. Using a Spatula, pull eggs in slow, sweeping strokes — lift and fold rather than stir constantly. This builds larger, softer curds. More frequent stirring gives smaller, more uniform curds. Total cook time: 3–6 minutes. Low heat = 5–6 min, creamiest result. Medium heat = 3–4 min, slightly firmer. Remove when almost no liquid egg remains but the surface still looks slightly wet and shiny.

Pour the batter into the prepared Springform Pan and smooth the top with a Spatula. Bake at 325°F for 30–35 minutes, until the top is set and slightly crackled and the center no longer jiggles when gently shaken.

Remove the cake from the Oven and let it cool completely in the pan on a wire rack, at least 20–30 minutes. The cake will sink slightly in the center as it cools — this is normal. Run a thin Knife around the edge before releasing the springform ring.