Heat a large pot to medium low. Add a bit of olive oil and add onions, garlic, and tomato paste, cook until it starts to brown on the bottom of the pan.
Whisk in the milk and 2 cups of water. Bring to a simmer. Whisk in the cornmeal and 1/2 teaspoon of salt. Once it's thoroughly mixed, add in the can of tomatoes.
Stir regularly and adjust the heat so it bubbles gently and continue cooking for 20 minutes.
In the meantime, Heat a skillet add a bit of oil and all the spinach and a pinch of salt, stir to wilt.
Add the shrimp to the skillet with salt and pepper and cook for 90 seconds or so until shrimp are no longer pink. Add lemon and parsley as desired.
Stir the cheese into the polenta, reserving half for garnish.
Servings 4