1. Preheat the oven to 400°F.
2. Lightly grease a 9-inch round pie plate, with some of the melted butter.
3. Scatter half of the raspberries and blackberries over the bottom of the dish.
4. Unroll the fillo dough and keep covered with a lightly damp towel while working to prevent the dough from drying and cracking.
5. Place one layer of the fillo sheet onto your work surface and evenly but lightly brush the melted butter over.
6. Using your fingers, gather the fillo and lightly scrunch to make a rope and then roll into a coil resembling a rose, place in the centre of the greased dish on top of the berries. Repeat this process until the dish is full of fillo roses. Then using 1-2 more buttered fillo sheets as necessary, scrunch and rip of pieces to nestle and fill in any visible gaps in the dish.
7. Lightly brush the remaining melted butter on the surface of the roses in the dish and bake in the preheated oven for 18-20 minutes until the top of the fillo is evenly golden brown.
8. While the fillo roses are crisping, prepare the custard: whisk together the egg, egg yolks, and the honey until even and smooth.
9. Add in the whole milk, heavy cream, vanilla extract, ground cinnamon, and lemon zest. Continue to whisk until even.
10. Once the fillo roses are evenly golden brown on top, remove from the oven and carefully pour in the custard mix, making sure to not cover any of the crispy edges on top. Allow a few seconds between pours to let the custard settle and absorb before pouring more, it should come up ¾ of the way of the casserole dish.
11. Place back in the oven and continue baking until the custard is set, approximately 12-15 minutes. You will know that the milk pie is ready when it springs back when lightly pushed on.
12. Remove from the oven and allow to cool for 5-10 minutes.
13. Top with the remaining berries as well as a dusting of the powdered sugar and some fresh mint leaves. Cut into wedges and serve while still warm or room temperature