Heat the vegetable broth in a medium saucepan on low.
In a large Dutch oven, wok, or sauté pan, heat the olive oil on medium heat. Add the diced onion and fry until soft and translucent. Add the dry arborio rice and combine with the onions and cook for 2 minutes.
Add the white wine to the risotto, and simmer on medium heat until it has absorbed, stirring occasionally.
Once the wine has absorbed, add a ladle of the broth and combine. Simmer until the broth has absorbed, stirring occasionally. Add the next ladle of broth and continue in this manner until you have used all of the broth, or the risotto is tender and creamy.
While the risotto is cooking, bring a large pot of salted water to boil. Add the broccoli rabe and boil for 3 minutes. Remove from the water and immerse the broccoli rabe into an ice water bath for 2 minutes. Drain, and chop into small pieces. Set aside.
Once the risotto has cooked, stir in the broccoli rabe, and season with salt, pepper, and the Parmigiano-Reggiano cheese. Let the risotto cool before you make the risotto balls or store in the fridge overnight.
In a medium saucepan, add enough oil to measure 4 inches deep. Heat on medium to 375 degrees F.
In a small bowl, whisk the flour and water, to make a slurry.
In a food processor, pulse the panko for a few minutes to get a smaller crumb. Place onto a plate.
Scoop ¼ cup of the risotto into your hands. Flatten into a disk and place a ½ inch piece of mozzarella in the center. Fold the risotto around the mozzarella and roll into a ball. Dip the ball into the flour slurry, and then cover with panko crumbs. Place the risotto balls onto a baking sheet.
With a slotted spoon, place 5 risotto balls at a time into the hot oil. Fry until golden brown, approximately 5-7 minutes. Remove and place on a paper towel to drain excess oil. Serve warm with marinara sauce. Best if eaten the day of.
In a large frying pan, heat the olive oil on low. Add the garlic and cook until it starts to sizzle, approximately 1 minute. Do not let the garlic brown. Add the canned tomatoes, basil, and salt.
Simmer for 15 minutes, or until the sauce has thickened. Serve warm.
Store leftover marinara covered in the fridge for up to a week.