Preheat oven to 350ºF.
Using a sharp paring knife, carefully cut around the outline of the pumpkin stem. You will want to do a hole big enough so you can reach inside. Remove the stringy part and seeds, and discard.
In the food processor (or a mortar and pestle), combine 1/2 onion, 2 garlic cloves, 2 tablespoons olive oil, salt and pepper. Process until it gets to a paste-like consistency. Spread that mixture all over the insides of the pumpkin.
Rub the pumpkin outside with 1 tablespoon olive oil. Close with the top part and roast for 45 to 50 minutes, or until the pumpkin is starting to get soft. Remove from oven and reserve, discarding the top or reserving for decoration.
While the pumpkin is roasting, prepare the shrimp stew. Start by seasoning the shrimp generously with lime juice, salt and pepper.
In a large Dutch Oven, heat 2 tablespoons of olive oil over medium-high heat. Once hot, add the shrimp and sauté until cooked, about 2-3 minutes per side. Be careful not to overcook it! Remove (along with any release juices) and reserve.
Reduce heat to medium and wipe the pot if needed. Add another tablespoon of olive oil and, once hot, sauté the remaining chopped onion and garlic, until translucent, about 2-3 minutes.
Add the chopped tomatoes and cook, stirring occasionally, until soft, about 6-8 minutes. Season with salt and pepper.
Stir in the flour and mix until incorporated.
Add the milk and cook, stirring constantly, until thickened, about 5 minutes.
Once thickened to the desired consistency, stir in the heavy cream and 1/3 cup chopped parsley. Return the shrimp (and juices) to the pot, stirring to combine. Taste and adjust seasoning if needed. Remove from heat and reserve.
Wipe the inside of the pumpkin with a paper towel, to get rid of any excess liquid.
Spread the cream cheese inside the pumpkin, all over the bottom and sides.
Fill the pumpkin with the shrimp stew, top with the parmesan cheese and bake for 15-20 minutes or until the pumpkin is soft and the top is bubbly and golden.
Garnish with the remaining parsley and serve, with white rice.