Preheat oven to 375˚F. Line a baking sheet with parchment paper.
Roll out pastry dough on a floured surface to a 1/8" thick circle. Trim and gather edges, reworking them into a disc to use for making decorations for the crust. Roll extra dough and cut out decorations with cookie cutters or freestyle using a knife or exact-o-knife. Roll up crust gently onto rolling pin and transfer to the baking sheet.
Cut pears in half lengthwise, keeping the stem intact on one half. Remove seeds with a paring knife or melon scoop. Thinly slice pear halves that have the intact stems, so as to keep the slices attached, and then fan them out. Thinly slice the other two pear halves and set pears aside.
Mix together remaining ingredients in a mixing bowl. Spoon mixture onto the center of the pie crust, leaving a 2" overhang of crust, and saving some of the mixture to drizzle over pears after you arrange them.
Arrange pears over the cranberry mixture, fanning and spreading them out. Fold the edges of the crust over the filling, tucking and overlapping as needed. Drizzle the remaining cranberry mixture over the pears.
Brush crust with non-dairy milk and attach the decoration cut-outs. Brush the tops of decorations with non-diary milk.
Bake at 375˚F for 45-50 minutes on the middle or upper third rack, until galette is bubbling and pears are fork tender. Remove from oven and allow to cool on a cooling rack for 30 minutes before cutting, so filling sets. Serve warmed or at room temperature. Remove split vanilla bean when serving.