Generously grease 4 ramekins with 1 tablespoon butter. Set aside.
Place bread cubes in a single layer on a baking sheet and bake in the preheated oven until dry, about 20 minutes.
Preheat oven to 400 degrees F (200 degrees C).
Melt 1 tablespoon butter in a skillet over medium heat. Stir in onion and salt; cook, stirring, until onions are light golden brown, 5 to 7 minutes.
Stir chicken stock, cream, thyme, and black pepper into skillet; bring mixture to a boil and remove from heat.
Stir bread cubes and chicken stock mixture in a large bowl until well combined. Stir in 1 ounce crumbled gorgonzola cheese. Divide mixture evenly between 4 prepared ramekins. Top each with a small crumble of gorgonzola.
Bake in the preheated oven until golden brown, 15 to 20 minutes.