Heat a large skillet over medium-high heat. Add the olive oil, garlic, fennel, salt, and pepper and stir until fennel is toasted and garlic is fragrant.
Add the frozen spinach and cook until the spinach has thawed and all of the moisture has evaporated.
Transfer the spinach to a medium bowl and allow it to cool while you prepare the crust.
Melt the butter for the phyllo crust in a small bowl and then stir in the olive oil. Brush the butter mixture over the pie plate to grease the interior.
Roll out the phyllo sheets and cover them with a towel. Remove one sheet at a time and place it over the pie plate, allowing the excess to drape over the sides. Brush the top of the phyllo with the butter mixture.
Build the crust, layer by layer, by draping each sheet of phyllo and brushing with butter until all sheets have been used. Lay the sheets in a cross pattern, then opposing diagonal pattern so that you get a sort of star and ensure all of the pie plate is covered.
To the cooled spinach add the cheeses and stir to combine. Spread the spinach mixture over the phyllo crust. Roll and crumple the excess phyllo layers to form a edge all around the pie. Brush the edge with any remaining butter mixture.
Bake, uncovered, for 25 minutes. Check the crust to make sure it isn't getting too dark and add foil if necessary. Bake an additional 15 minutes. Remove from the oven and allow to cool for 10 minutes.
Using a broad spatula (or two), remove the pie from the plate and place it on a cutting board. Slice it into wedges with a serrated knife.
Nutrition facts are sometimes provided below and are calculated using an online calculator. With specific brands of ingredients and additions, omissions, or substitutions the nutrition facts may change. We encourage you to use your own nutrition facts caculator to obtain the most accurate nutrition facts for your meal.