Preheat your oven to 400 degrees Fahrenheit and prepare a large baking sheet by lining it with parchment paper.
Wash the pumpkin and cut it into large slices, leaving the skin on and scraping out the seeds and insides of the pumpkin.
Place the pumpkin slices flesh side up (skin side down) on the baking sheet and sprinkle with the 1/2 teaspoon sea salt.
Roast at 400 degrees Fahrenheit for about 25-35 minutes, or until the pumpkin flesh is soft and beginning to brown slightly around the edges (test with a fork for softness).
When the pumpkin is almost done roasting, heat a large pot over medium-low heat and add the butter.
Add the garlic, onion, sea salt and white pepper and stir together, cooking until the mixture is fragrant and the onion is translucent.
Add the white wine and continue cooking as the wine cooks off and at least half of the moisture evaporates.
When the pumpkin has finished roasting, scrape the pumpkin flesh out of the hardened skin and into the pot with the onion mixture.
Add the chicken broth slowly, just until the liquid level reaches about a half-inch below the top of the pumpkin. Adding too much liquid will make the soup too liquid-y, so only add what you need (every pumpkin is slightly different in size, so this measurement might vary slightly).
Stir the soup well and cover, cooking on medium-low heat for about 15-20 minutes, stirring regularly.
Turn off the heat and allow the soup to stop boiling. Add the heavy cream and puree with a hand blender on high speed until creamy and smooth (or transfer to a regular blender and puree on high speed).
Serve immediately with a drizzle of cream and a few pumpkin seeds for garnish.
Store in an airtight container in the fridge for up to three days, or freeze in a freezer-safe container for up to a month.