Thaw spinach and pat dry with paper towels
In a pot over the stove, heat milk, butter, and salt until butter melts and mixture comes to a boil.
Remove from heat and add flour. Mix with a wooden spoon until dough forms and sides of the pan are clean.
Add eggs one at a time, mixing well after each addition.
Add cheeses and spinach and combine.
Spoon onto lined cookie sheet at least one inch apart.
Bake on 375 for 15-20 minutes
Serve warm for best results!