Mix together softened cream cheese, drained and chopped artichoke hearts, cooked and drained spinach, sour cream, parmesan, mozzarella, garlic salt, salt, pepper, red pepper flakes and vinegar (if using) in a bowl. Set aside.
In a small bowl or measuring cup, combine the warm water, 1 tablespoon sugar and yeast; whisk and set aside to proof. If the mixture is not bubbly and doubled in volume after 5-10 minutes, toss out and start again with fresh yeast.
In a large mixing bowl, whisk all dry ingredients for pastry together (gfJules Flour, baking powder and salt). Add small cubes of butter and mix with a pastry blender or a paddle attachment with a stand mixer until the butter is cut throughout the dough and the flour looks pebbly.
Add the milk and eggs and beat until integrated. Stir in the proofed yeast-sugar-water mixture, then beat another minute, until the dough comes together and is not too sticky or tough. If the dough seems resistant, dry or tight, add more warm water by the tablespoon and knead into the dough until it is soft but not too sticky.
Prepare a large baking sheet by lining with parchment paper. Turn the dough out onto a silicone pastry mat or onto a clean counter dusted lightly with gfJules Flour.
Divide the dough in half and roll one half of the dough gently out into a circle the size of a large dinner plate; cut off any raggy edges to make the circle even, if you prefer. Using bench scrapers or spatulas, lift the dough and transfer to the parchment-lined baking sheet. Spoon the filling out onto the rolled round, covering all of the dough.
Click on the photo above the recipe card to watch the quick how-to video on making this gorgeous pull-apart bread.
Repeat the rolling process with the other half of the dough. Lift and transfer it to top the other dough with filling. Place a drinking glass in the center of the pastry, then cut just into the glass to form 12 evenly spaced strips of stuffed dough. Gently lift up on the end of each strip and twist. (see video)
Brush pastry with egg wash of one beaten egg + 1 tablespoon water, or warm milk of choice.
Cover with oiled wax paper or parchment and set in a warm place to rise for 30 minutes.
While the pastry rises, preheat oven to 350º F (static) or 325º F (convection).
After rising, remove paper and place pastry in the oven to bake for 20 minutes, or until lightly browned and a toothpick inserted into the pastry comes out clean.
Remove to cool on a wire rack before serving.