To make the pumpkins: Beat together 1 cup peanut butter, the butter, and 1-2 cups powdered sugar until combined. Roll the dough into 1-inch balls and place on a parchment-lined cookie sheet.
Insert a cinnamon or pretzel stick into the center of each dough ball. Drizzle chocolate around the cinnamon stick to look like a stem. Sprinkle with black sanding sugar. Chill in the freezer until firm, about 30 minutes.
Meanwhile, line a cookie sheet with parchment paper. Spread half the chocolate into a thick layer. Add small spoonfuls of the remaining peanut butter, then cover the peanut butter with chocolate. Arrange the pumpkins over the chocolate. If making/using the white chocolate pretzels, decorate as desired. Chill the bark until firm, at least 30 minutes to an hour.
Break into pieces and serve! Keep chilled in the fridge.
