Prepare the Dough: In a food processor, combine gluten-free multi-purpose flour, granulated sugar, baking powder, and kosher salt. Cut cold unsalted butter and full-fat cream cheese into small cubes and pulse until resembling coarse crumbs.

Incorporate Wet Ingredients: Slowly add cold milk and vanilla extract. Pulse until mixture forms a slightly sticky dough.

Chill the Dough: Shape dough into a rectangle, wrap in plastic wrap, and chill for 10-15 minutes.

Roll and Fold the Dough: Roll chilled dough to ¼ inch thick, perform a tri-fold technique, and chill again for 10 minutes. Repeat this folding process twice more.

Prepare the Chocolate Filling: Preheat oven to 400°F. Chop dark chocolate, mix with cocoa powder and light brown sugar.

Assemble the Rugelach: Roll out chilled dough again, brush with melted butter, and sprinkle chocolate filling evenly.

Shape the Rugelach: Roll from one edge to form a log, slice into 1-inch pieces and place on a parchment-lined baking sheet.

Bake the Rugelach: Brush with beaten egg, sprinkle with coarse sugar, and bake for 20-24 minutes until golden brown.