Wilt and chop the spinach. Place 1/3 of the washed spinach in a paper towel. Roll up the towel, moisten slightly and microwave for about 45 seconds. Repeat until all the spinach is wilted. Roughly chop and set aside.
Preheat oven to 350 degrees.
Finely dice a shallot. Grate 1/2 cup of good quality Parmesan cheese divided in half.
Melt 1 Tbsp. butter in a heavy bottomed skillet. Add the shallot and cook for 3 to 4 minutes over medium heat. Do not brown the shallots, but cook until just softened.
Reduce heat to low and add the Boursin cheese to the skillet breaking it up into pieces. As soon as the Boursin begins to melt, add the cream and 1/4 cup Parmesan to the skillet. Cook, stirring often until the sauce becomes thick and creamy; about 2 minutes longer.
Gently add the chopped, wilted spinach into the sauce stirring to ensure all the spinach gets covered evenly. Increase the heat until the sauce just begins to bubble and then remove from the heat.
Generously butter a small baking dish. Pour in the spinach and sauce and cover with Panko bread crumbs pressing the crumbs lightly into the spinach mixture. Cover with remaining 1/4 cup Parmesan and bake for about 20 minutes.
If you want a browner crust, broil for a couple of minutes, but watch closely so it doesn't burn.