Prepare the crisps:
1. Preheat the oven to 350 F. In a small bowl, combine the toasted sesame seeds, dried oregano and salt. Mix well.
2. Line a work surface with parchment paper. Working directly on the parchment paper, place 1 sheet of fillo. Generously brush the entire surface with the melted butter. Place another layer of fillo directly on top using hands to smooth out any air pockets and brush again with the melted butter. Repeat this process three more times. On the top layer, brush with the beaten eggwhite then sprinkle evenly with the sesame oregano mixture.
3. Using a pizza cutter or knife, cut into 48 pcs (8x 6 rectangles). Slide the entire parchment paper onto a baking sheet and bake in the oven for 10-12 minutes until crispy and golden brown. Store the crisps in an airtight container for up to three days
Prepare the dip
1. Preheat the oven to 375 F.
2. Heat a pan on medium heat. Add in the olive oil, onions and garlic. Cook until softened and light golden brown. Stir in the spinach and season with salt and pepper.
3. In a mixing bowl, combine the sauteed spinach, ricotta cheese, feta cheese, and half of the mozzarella cheese. Stir to combine and transfer to an ovenproof dish. Top with the remaining mozzarella and bake in the oven for 12-14 minutes or until bubbly and golden.
4. Serve with fillo crisps while dip is still warm