Line an 8x8-inch pan with parchment, letting it overhang for easy lifting. Lightly mist with oil if you like.

In a microwave-safe bowl, combine chocolate and nut butter. Heat in 20–30 second bursts, stirring between, until smooth. Do not overheat.

Whisk in maple syrup, vanilla, and a pinch of salt while the mixture is still warm.

In a separate bowl, whisk Greek yogurt until silky. If using protein powder, whisk it into the yogurt until smooth.

Fold the chocolate mixture into the yogurt. Stir gently but thoroughly until the color is even and no streaks remain.

Taste and adjust sweetness. Add any mix-ins now (save delicate toppings for later).

Spread the fudge mixture into the lined pan. Smooth the top. Sprinkle with sea salt flakes or toppings if using.

Refrigerate for at least 3–4 hours, or until firm. For the cleanest cuts, chill overnight.

Lift out using the parchment and slice into 16–25 squares. Wipe the knife between cuts for neat edges.