Heat the 1 stick of butter in a pot just until it melts. Melt the rest of the butter in microwave for 20-30 seconds and let cool.

As soon as it has melted, add the flour and start mix with a hand whisk.

Add the milk in small batches while whisking continuously. Wait for each batch of milk to be completely incorporated into the mixture before adding the next one.

Let the béchamel sauce simmer for a bit and add a generous amount of freshly ground pepper. When béchamel begins to bubble, take it off the heat.

Add the grated gruyere cheese and stir with a spatula. As soon as the gruyere melts and is combined, add the feta cheese. Stir.

Taste and adjust salt and pepper, if needed.

After the cheese has been incorporated the béchamel should be cool enough to add the eggs and stir to combine aggressively so the . Set aside until needed.

Preheat oven to 375ºF.

Grease a 30x40 cm baking pan.

Spread one sheet of phyllo on the bottom of the pan and drizzle with melted butter.

Divide package of phyllo dough in half. Set one half aside covered with a damp towel so they don’t dry out.

So drizzle each phyllo with melted butter, roughly fold together and add to the baking pan.

Repeat process until this half of the phyllo dough has been added, all roughly folded and set one next to the other, gently in the pan.

Pour the béchamel sauce carefully over the folded phyllo dough without pressing on them or flattening them.

Repeat the same process with the remaining half of the phyllo dough that was set aside, apart from 2 sheets which should be added spread out, as a top layer.

Score pie and pour soda water over it. Set aside for 5 minutes.

Bake for 60 minutes, until phyllo is golden and crunchy.