Preheat oven to 375 degrees F.
Melt butter in a 9” oven proof skillet over medium high heat (OR use any skillet and transfer dip to lightly greased 9” pie pan to bake). Add onions and cook, while stirring for 3 minutes. Add garlic and saute 30 seconds.
Stir in flour, and cook, while stirring, for 2 minutes. Turn heat to low and stir in milk, Worcestershire sauce and all spices. Increase heat to medium high and bring to a simmer, while stirring, until thickened (but not too thick).
Remove from heat and stir in sour cream until smooth. Stir in spinach and roasted peppers followed by brie, 1/2 cup mozzarella, 1/2 cup Jack cheese, and 1/4 cup Parmesan.
Smooth dip into an even layer (or transfer to prepared pie pan and smooth). Top with remaining cheeses and bake 15-20 minutes or until bubbly and brie is melted. Broil until cheese is golden.
Let sit at least 5 minutes then serve hot with bread, crackers, etc.