If you’re into pistachios, I recommend toasting them to enhance the flavor. Heat a small skillet over medium heat. When hot, add the pistachios and cook for a minute or two, shaking the pan regularly, until the nuts are toasted and fragrant. (Be careful not to burn them!!) Transfer to a small bowl to cool while you prep the filling.
Place the yogurt, mascarpone, honey, lemon zest and juice in the bowl of a food processor. Process until well combined and slightly fluffy. You can also combine the ingredients in a mixing bowl and use a hand mixer to whip the ingredients together, or simply whisk them by hand. (The latter method requires some upper body strength, but it’s doable.)
Add about a teaspoon of filling to each phyllo shell. I use the base of a spoon or fork to do this (a spoon can be a little to wide for the shells), but you could also use a pastry bag to pipe filling into each shell.
Top the filling with a few berries (I recommend cutting blackberries in half and strawberries into quarters) and sprinkle with toasted pistachios if using.
Serve immediately or refrigerate for up to 3 hours. (The filled phyllo shells tend to get soggy in the fridge after a few hours.)