Start by stirring together the plain Greek yogurt, peanut butter, vanilla protein powder, maple syrup or honey, and vanilla extract in a mixing bowl until smooth and creamy.

Spread the mixture evenly onto a parchment-lined quarter sheet pan, aiming for a thickness between 1/4 inch and 1/2 inch.

Microwave the dark chocolate chips in 30-second increments while stirring until fully melted, then pour and spread the chocolate evenly over the peanut butter yogurt mixture.

Place the bark in the freezer for at least 2–3 hours until completely set, then sprinkle with flaked sea salt if desired and cut into pieces.