Heat broth and milk in pot until simmering.
Slowly whisk in cornmeal; stir to avoid lumps.
Reduce heat; stir every few minutes for 25–30 min until thick.
Stir in butter and parmesan; season with salt & pepper.
Clean and slice mushrooms.
Heat olive oil in skillet, add mushrooms, cook 3–4 min.
Add garlic, thyme, deglaze with wine; finish with cream.
Taste, adjust seasoning; top polenta with mushrooms.
Garnish with parmesan, herbs, truffle oil if desired.