Check to see that one rack is in bottom third of oven and heat oven to 425 degrees F. Measure milk in a 2-cup measure, add sugar and egg yolk, stir to mix well. Stir in dried fruit. Let stand until ready to use.
Put flour, baking powder, spice, and salt into a large bowl, stir to mix well. Add butter and cut in with pastry blender or rub in with fingers, until mixture looks like fine granules. Stir milk mixture and pour over flour mixture. Stir with a fork until a soft dough forms. Turn out dough onto a lightly floured surface and give 10 kneads. (If very sticky, let stand 3 or 4 minutes or add a little more flour.) Cut off about one-fourth of the dough.
Put remaining dough on an ungreased cookie sheet at least 16 inches long. Using both rolling pin and fingers, pat and roll dough into a flat triangle about 12 inches long and 9 inches wide across the bottom. With scissors, make about ten diagonal cuts down each long side of the triangle, cutting to within about 1 inch of the center.
Shape a small piece of reserved dough into a trunk at bottom of tree and remaining dough into a "pot." Dough may now be covered with plastic wrap and refrigerated for a couple of hours or frozen for up to 2 weeks.
Bake tree 10 minutes. Beat egg white with a fork until broken up. Brush over hot bread, sprinkle with sugar. Bake 5 to 8 minutes longer, until light brown. With two spatulas, carefully transfer tree to a wire rack. If possible, cool at least 2 hours before serving. Let guests break off small pieces.