Preheat oven to 425 degrees Fahrenheit. Line a cookie sheet with parchment paper to place your galette for baking.
Roll out the pie crust out to a 12 in. circle. It does not have to be a perfect circle, but make sure the ends to not tear. Place your dough onto the cookie sheet.
In a medium mixing bowl, combine cranberries, raspberries, blueberries, lemon zest, vanilla, and salt. Mix until all the ingredients are well incorporated.
Pour in the fruit mixture into the middle of your dough, but make sure to leave 1 ½ inches of crust around the edges.
Fold the edges of your crust dough over the fruit mixture, pinching the folds together to prevent it from unfolding. The center top of your fruit mixture should remain exposed.
Place it in the oven for 30-35 minutes or until the crust is golden brown.
Allow it to cool for 20 minutes before placing it in a serving dish and top with fresh mint leaves and pistachios. Serve warm.