Place oven on 400 degrees
Place the vegetables on lined baking sheet, roast for 30ish minutes
Place sliced Polenta on lined baking sheet and bake with vegetables, bake for 30 min with vegetables, flip half way.
For Sauce. melt butter and olive oil in a pan. Add Garlic and Onions and saute for 2 minutes (careful not to burn). Add cornstarch and incorporate the oil. Add the Vegetable broth and whisk until smooth. Then add the milk, cream, herbs and salt and pepper. Whisk to make sure it's smooth. Cook on medium-high for 5-7min to thicken, but don't cook too long or it will get too thick (like mine in the picture).
Remove the Polenta and Vegetables from the oven and layer on a plate, drizzle sauce on top and garnish with Sliced black olives.
Enjoy!