Bring a large pot of water to a boil. Season the water with a few generous pinches of kosher salt. Prepare an ice bath by adding several cups of ice to a large bowl and then filling it with water; set aside. Add the green beans to the boiling water. Cook for 2 minutes. Using a slotted spoon, remove the beans from the pot and transfer them to the ice bath to stop the cooking process. Strain the beans and pat dry.
Add the green beans, corn, tomatoes, and bell pepper to a large bowl; toss to combine.
In the bowl of a food processor, add basil, garlic, Dijon mustard, maple syrup, and vinegar. Pulse until smooth. With the processor on, slowly drizzle in the olive oil. Season with salt and pepper to taste. Drizzle the vinaigrette over the salad right before serving. Garnish with shavings of Parmesan cheese and basil leaves.