How to Make It
Weigh or lightly spoon flours and cornstarch into dry measuring cups; level with a knife. Combine flours, cornstarch, xanthan gum, baking powder, and salt in a medium bowl, stirring with a whisk.
Place cream cheese, butter, and 2 tablespoons granulated sugar in a large bowl; beat with a mixer at medium speed until blended. Add 2 tablespoons milk and egg; beat until blended. Add flour mixture, beating until blended. Turn dough out onto a well-floured surface; knead until smooth and elastic. Divide dough into 2 equal portions, shaping each into a disc. Wrap each in plastic wrap; chill at least 3 hours.
Preheat oven to 375°.
Combine pecans, brown sugar, and 1/8 teaspoon cinnamon in a small bowl. Place 1 dough disc onto a piece of well-floured parchment paper. Cover with an additional piece of floured parchment paper. Roll dough, still covered, into a 10-inch circle. Remove top sheet of paper; spread 1/4 cup melted preserves over dough. Top preserves with half of pecan mixture. Cut circle into 8 wedges. Beginning with long side, roll up each wedge. Place rolls, point sides down, 2 inches apart on a baking sheet lined with parchment paper. Repeat procedure with remaining dough disc, preserves, and pecan mixture.
Combine 1 tablespoon granulated sugar and 1/4 teaspoon cinnamon in a small bowl. Brush each rugelach with milk; sprinkle with sugar mixture. Bake at 375° for 24 minutes or until golden brown. Cool completely on pan.