Preheat oven to 400°.
Squeeze excess liquid from the thawed spinach until it is as dry as possible.
In a skillet over medium heat melt butter, then add shallots and garlic and cook for 2-3 minutes until shallots become translucent.
Sprinkle flour into skillet whisking for 1-2 minutes until flour lightly browns.
Slowly add the heavy cream or milk, whisking continuously until the sauce begins to thicken, 3-5 minutes.
Stir in white cheddar cheese and Parmesan cheese.
Dice up 4 of the bacon strips and add to the cheese sauce. Stir until the cheese has melted.
Salt to taste.
Add spinach to the mixture and stir to combine.
Remove from heat while you prepare the puff pastry.
On a lightly floured surface, unfold thawed puff pastry. Roll each sheet into a 12-in. square. Cut each pastry sheet into nine squares.
Place in greased muffin cups, pressing gently onto bottoms and up sides, allowing corners to point up.
Fill each puff pastry cup with about 2 tablespoons of creamed spinach.
In a small bowl mix together the egg and water to make an egg wash.
Brush egg wash over the puff pastry then place in the oven and bake for 15-18 minutes or until puff pastry is golden brown.
Remove from oven and serve.