1. Crumble your feta into small crumbles. Combine the crumbled feta with the ricotta cheese, fresh chopped spearmint and the egg in a bowl. Stir until the mixture is well combined and homogenous.
2. Prepare your phyllo dough by carefully removing 10 sheets from the stack of dough (roll up any leftover phyllo and freeze to use another time). With the phyllo dough sheets in an even stack, cut them in half lengthwise to create two long rectangular strips of phyllo. Combine these strips into one stack and keep covered with a barely damp linen towel (I use a spray bottle of water to barely moisten the linen).

TO ASSEMBLE:

1. Carefully remove one sheet of phyllo from the stack (cover the remaining phyllo to keep it from drying out). Use a pastry brush to brush 1/2 the sheet of phyllo lengthwise with olive oil. Fold the phyllo over itself lengthwise in half and press to seal. You now have a long, narrow double-layered strip of phyllo.
2. Brush the phyllo dough again with olive oil. Use a spoon to scoop about 1 tbsp of cheese filling onto the bottom of the phyllo dough strip.
3. Starting with one of the bottom corners of the phyllo dough, gently fold up at a 45° angle to create a triangle (see the video above for a visual). Continue folding from the opposing corner to encase the cheese filling with phyllo.
4. Once the phyllo dough has been folded completely into a triangle, brush both sides of the triangle with a bit of olive oil and set it aside on a parchment-lined baking sheet.
5. Repeat this process until you have used all of the filling. (At this point you can freeze the cheese triangles for future use: simply freeze them while still on the parchment-lined baking tray until solid. Then layer the frozen triangles in an airtight container with sheets of parchment or wax paper in between layers to prevent them from sticking together).

TO BAKE:

1. Pre-heat oven to 375°F. Bake triangles until they are nicely golden, about 20-25 minutes. (If baking from frozen add an extra 5 minutes of bake time). Enjoy!