Cook the udon noodles according to package instructions, usually 3-5 minutes. Drain and set aside. In a saucepan over medium heat, combine the vegetable broth and coconut milk. Stir in the miso paste until fully dissolved and the sauce is smooth. Add minced garlic once the sauce is heated through but not boiling; cook for about one minute until fragrant. Add the cooked udon noodles to the sauce, tossing gently to ensure the noodles are well coated with the creamy miso sauce. Taste and adjust seasoning if needed. Divide the noodles and broth into serving bowls. Garnish with sliced green onions and serve immediately for best texture and flavor.