Melt butter in a large pot over medium heat. Add the diced onion and celery and cook for 4 to 5 minutes until softened.

Stir in the garlic and cook for 30 seconds until fragrant. Sprinkle in the flour and stir constantly for 1 minute.

Slowly whisk in the chicken broth until smooth. Bring to a gentle simmer and cook for 3 to 4 minutes until slightly thickened.

Reduce heat to low and stir in the heavy cream, Old Bay seasoning, salt, and white pepper. Simmer gently for 8 to 10 minutes, stirring occasionally.

Gently fold in the lump crab meat, being careful not to break up the chunks. Add the dry sherry and cook for 2 to 3 minutes until heated through.

Finish with fresh lemon juice and chopped parsley. Ladle into bowls and serve immediately.