Preheat the oven to 450 degrees.
In a bowl, toss the tomatoes in the olive oil with a sprinkle of salt
Place mushrooms and onions into a baking pan lined with parchment paper.
Roast for 30-40 minutes until golden-brown, making sure to stir the pan every 10 minutes to keep the tomatoes from burning.
In a tall and narrow pot, bring chicken broth to a boil over medium heat.
Whisk in the polenta and stir well with a wooden spoon.
Reduce the heat and cook, frequently stirring until it thickens.
Season with salt and pepper to taste.
Transfer the polenta into a greased baking sheet and spread it evenly with a spatula.
Let it cool at room temperature.
Cut the polenta into small squares.
Preheat the grill on high heat.
Spray polenta squares with extra virgin olive oil and grill for a couple of minutes until grill marks form.
Flip the polenta squares on the other side and grill again for a couple of minutes. Remove and set aside.
Once tomatoes are done roasting, place on top of polenta squares, along with a spoonful of Burrata and fresh basil.
Serve and enjoy.