Bring 2 cups water to a boil in a medium saucepan. Slowly whisk in the polenta, garlic ,sage, parmesan, and season with salt and pepper. Stir until the polenta is soft and thick, about 3-5 minutes. Turn the heat off, cover the pot, and let the polenta sit 5 minutes.
Line an 8x8 square baking dish with parchment paper. Spread the polenta in an even layer in the dish. Freeze 15-20 minutes, until set, or 1 hour in the fridge.
Preheat the oven to 450F. Take the polenta out of the baking dish and cut into thin or thick "fries" shape. Spread some olive oil on a baking sheet. Place the fries on the prepared baking sheet and gently coat them with more olive oil. Spread the fries in an even layer. Transfer to the oven and bake for 15 minutes, then carefully flip. Bake for 15-20 minutes more until crispy.
Season with salt, some extra parmesan, and sage. Serve with a side of marinara sauce or ketchup. ENJOY!