Melt butter in a small sauce pan over medium heat. Mince or grate garlic and add it to the butter. Saute until the garlic starts to brown.
Whisk in flour until smooth. Whisk in heavy cream, sour cream, Parmesan cheese and a little bit of salt. Cook, stirring frequently, until the mixture just starts to boil. Take off heat.
Cut the shrimp into small pieces and spread them in the baking dish of your choice.
Pour the cream mixture over the shrimp and sprinkle with more Parmesan cheese.