Preheat oven to 375°F. Wash and score potato; bake until knife easily pierces, 40 to 55 minutes.
In mixing bowl, combine Gouda, egg yolks, cream, pepper, Old Bay seasoning, garlic and thyme. Gently fold in crabmeat.
Open potato; remove 1⁄4 of potato flesh; reserve for other use. Place crab mixture inside potato. Cover; bake at 375°F until all cheese melts. Remove cover for 2 minutes to lightly brown potato. Garnish with chives and rosemary.