Preheat oven to broil and line a sheet pan with parchment paper. Dress onions and corn with olive oil and season with salt and pepper. Place sheet pan in oven and toast green onions until charred, about 5 minutes, turning each one over at 2 minutes. Continue to broil corn until tender, about 20 minutes total.
Once the corn is tender and cool enough to handle, cut kernels off of the cob and cut up the green onion.
Bring a medium skillet to heat and render bacon until crispy. Drain and set aside.
Bring a 4 cup sauce pot to heat over medium heat. Add a touch of oil and saute shallot and garlic until translucent, about 4 minutes. Add polenta and toast for about 2 minutes, stirring constantly.
Add the cream and milk to polenta and stir frequently, making sure to remove polenta from edges and bottom of the pot. Keep stirring until polenta is thick, smooth, and creamy.
Add in parmesan, corn, green onions and bacon (set some bacon aside for garnish). Adjust seasoning.