Spray non-stick pan with cooking spray and heat on medium. Once pan is hot, place banana halves cut side down in pan with walnuts. Fry until bananas are caramelized and walnuts are toasted, 1-2 minutes. Flip bananas over and stir walnuts. Fry for an additional 1-2 minutes. Remove from heat.
Heat dark chocolate chips in microwave at 30-50% power safe dish in 15 second intervals until melted, stirring well after each interval.
Add Greek yogurt evenly into 2 small bowls. Top with bananas and walnuts. Drizzle with dark chocolate. Serve.