Make the rugelach dough. Pulse together all-purpose flour with sugar, salt, butter, cream cheese, and sour cream in a food processor until the mixture forms a rough dough. Shape the dough into two discs, wrap in plastic, and chill in the fridge for 1 hour or until firm. Alternatively, chill in the freezer for 30 minutes or until firm.
Meanwhile, make the filling. Combine dried cranberries with water, brown sugar, cinnamon, and vanilla extract. Bring to a simmer over medium heat and continue to cook until all the liquid is absorbed, about 15 minutes. Remove from heat and blend the mixture with strawberry preserves until smooth. Add chopped toasted walnuts and mini chocolate chips, stirring to combine. Let cool.
Take out one of the discs from the fridge. Dust a clean work counter with flour and roll the dough into a rectangle, about 12x8 inches. Spread ½ of the filling on the dough, leaving a ¼ inch border on the long side facing away from you. Roll the dough into a tight log, starting with the long side facing you. Place on a lined baking sheet and return to the refrigerator to chill. Repeat with the remaining dough.
Preheat oven to 375 degrees F.
Remove the logs from the refrigerator and slice into 1 ½ inch pieces. Place the cookies seam side down on lined baking sheets. Brush the tops of the rugelach with milk and sprinkle coarse sugar on top. Bake for 20-25 minutes or until golden brown. Remove from oven and cool on wire racks.