In a medium mixing bowl, combine 1 cup Greek yogurt, 2 tablespoons cocoa powder, 1 tablespoon honey, and 1/4 teaspoon vanilla extract until smooth and fully incorporated.
Slice 1 ripe banana into 1/4-inch thick rounds, reserving a few slices for garnish.
Gently fold most of the banana slices into the yogurt mixture until evenly distributed throughout.
Spoon the yogurt mixture into a serving bowl, creating a smooth surface on top.
Sprinkle 1/4 cup granola and 1 tablespoon chopped walnuts over the yogurt mixture.
Arrange the reserved banana slices on top and finish with a pinch of sea salt for balance.