Zest the orange and lemon. Juice the oranges and measure out 200 grams (about 3/4 cup plus 1 tablespoon).

In a saucepan, bring all the syrup ingredients except the honey to a boil for a few minutes. Add the honey and let the syrup cool completely.

Make a well in the center and add the orange juice (after dissolving the baking soda in it), water, brandy, and ground mastiha. Whisk until the mixture is smooth and combined.

Brush a 9.5-inch (24 cm) round baking pan with olive oil.

Layer 2 sheets of phyllo in the pan, covering the sides as well, brushing each sheet with olive oil. Trim any excess. Crumple the next 2 sheets and place them in the pan, brushing with oil. Lay the next 2 sheets flat. The phyllo sheets are larger than the pan, so 4-5 sheets are enough for 6 layers. You don't need to use whole sheets for each layer.

Pour the batter over the phyllo, which will have started to rise. Fold the edges of the phyllo over so they don't stick out. Sprinkle with sliced almonds. Let it rise for about 20 minutes, then bake in a preheated oven at 340-355°F (170-180°C) for 30-40 minutes.

As soon as you take it out of the oven, pour all the cold syrup over the dessert. It will absorb it all, even if it seems like a lot. Once cooled, cut into diamond shapes and enjoy.