In a medium to large sauce pot, add 3 tbsp of butter and cook over medium heat.
Once the butter is melted, add in the diced shallots and minced garlic. Cook until fragrant, approximately 2-3 minutes. Stir often. Watch is closely so it does not burn.
Turn the heat down to medium low. Add the dry pasta into the pot and mix it in the melted butter, garlic and shallot until they are coated.
Add 2 cups of vegetable broth into the pot and mix. The shells may not be fully covered. Mix to coat the shells then cook for 5 to 7 minutes, stirring very often, until the shells start to plump up and most of the liquid is absorbed.
Once the vegetable broth is cooked down, add another 1 cup of vegetable broth and mix . Stir the mixture every 1-2 minutes until it is cooked down again. It will take about 5 minutes.
Repeat adding the vegetable broth and cooking it down one more time until the pasta is fully cooked.
While the pasta is cooking, prep the cheeses. Remove the rind from the brie cheese and cut it into cubes. Shred the parmesan and cheddar cheese if it is not pre-shredded.
Once the pasta is fully cooked, remove it from the heat (keep it in the hot pot) and add the brie cheese, parmesan cheese, cheddar cheese, pepper for taste and heavy cream. Stir until all of the cheese is melted and a creamy sauce develops. It will be a little hard to stir at first but once the cheese melts it will get easier.
Add to serving bowl. Option to top with breadcrumbs* or herbs.