Make puff pastry, if you are doing it from scratch. Stir together flour and salt in a large bowl. Cut butter into small pieces and add to the bowl. Pour in water gradually, while stirring the mixture - add just enough water to get everything combined into a rough dough. You don't want the butter creamed into the flour, you want it to stay in chunks - this is what causes the dough to form those beautiful, flaky layers in the oven.

2. Turn the mixture out onto a floured surface. Form it into a rectangle, and gently roll out until it's about a half inch thick. Fold the bottom third up into the middle, and fold the top third down on top of that. Turn it 90 degrees, add more flour to prevent sticking, and roll it out again. Repeat this process three more times, adding flour as needed. Wrap the dough in plastic wrap and refrigerate while you prepare the filling. You can also freeze it for about 10 minutes before using, if your filling is already made.

Note: While making this dough, you need to work quickly, with very cold water and butter, to prevent the butter from melting into the dough. 

3. Make the spinach and artichoke dip. Start with the Mornay sauce. Stir together 3 Tbsps butter and sour cream in a sauce pan over medium heat. Stir together cream and corn starch in a small bowl and add to the pan. Let the sauce come to a boil, stirring constantly. When it reaches a boil, turn off the heat and gradually stir in the shredded cheese, until sauce is smooth. It should be fairly thick. 

4. In a skillet, cook onion over medium heat in the remaining 1 Tbsp of butter until it starts to become translucent. Add spinach, garlic, artichokes, thyme, and salt. Let cook for roughly five minutes, stirring occasionally, until the artichokes start to soften. Pour cheese sauce over the vegetables and stir until well combined.

5. Prepare your Tarte Soleil. Take half of your puff pastry (leave the other half in the fridge)  and roll out into a 12 inch round on a floured surface. Take a round plate slightly smaller in diameter than your baking tray (I used a pizza tray) and place it upside down on the dough. Trace around it with a knife to form a perfect circle for the base of your Tarte. Place the circle on your baking tray (lined with parchment paper).

6. Top with a generous layer of filling, leaving about a half inch bare around the outer edge of the circle. You may have some extra filling - don't feel like you need to use all of it, you just want a nice thick, even layer - no gobs. Cover with plastic wrap and refrigerate while you work with the rest of the puff pastry.

6. Roll the second half of your pastry dough into a 12 inch round and cut a perfect circle as you did with the first layer. Place this layer on top of the first layer with the filling, so that the filling is sandwiched between the two layers. Place a small bowl or glass in the center of the the dough. This will mark the center of your Tarte, the section that doesn't get cut and twisted. 

7. Cut away from the glass with a knife, slicing the dough into quarter sections. Cut each quarter section in half, and each of those sections in half again, until you have 16 total sections. You can choose to go a step further, cutting each section in half one more time, to end with 32 total sections coming from the center circle. It mostly depends on how many servings you want to make/how much work you want to do. Be careful not to cut through the parchment paper. 

8. Twist each section 3-4 times, twisting all of the sections in the same direction. Don't just hold the end of a section and twist, because the dough won't automatically twist the way you want it to. The best way to do this is to try to twist each section once near the center circle, once in the middle of the section, and once closer to the end, so they're evenly spaced. 

9. When all of the sections are twisted, you should have a beautiful sunburst. Beat egg in a small bowl and brush over the pastry. Bake at 350 degrees for 30-35 minutes, until golden brown. Let cool before moving to a serving tray, to prevent Tarte from tearing.