A Scottish tradition for centuries, this fruit-filled bread is found in the windows of bakeries during the holidays. Home versions these days are often made with pie pastry surrounding a fruitcake, but here we hark back to the older, yeast-based version, baked up as smaller, gift-sized loaves.
To make the dough: Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Combine all of the dough ingredients, mixing and kneading until a soft dough forms. Cover and let rise until doubled, 1 1/2 to 2 hours.
Divide the dough in half. Put half into a bowl, cover, and refrigerate. Put the remaining half back in the mixing bowl, and mix in all of the filling ingredients. This will be quite messy at first, but the dough will come together as you continue mixing.
Once the filling is thoroughly mixed into the dough, divide it into six equal pieces. Shape each piece into a ball as best you can; it will be sticky; wetting your hands first will help with this.
To assemble: Remove the reserved dough from the refrigerator and divide it into six equal pieces. Round each into a ball, cover, and let rest for 10 minutes.
Grease the wells of an oversized muffin pan, or line a baking sheet with parchment.
Roll each ball of dough into a 6" round, about 1/2" thick; make the edges thinner if you can (a tapered pastry pin is best for this). Place one of the balls of filling in the center, and bring the edges up and around to meet on the top, overlapping to enclose the filling as needed. Pinch the dough together and place, pleated side down, in the wells of the prepared pan or on the baking sheet. Repeat with the remaining dough and filling.
Cover the buns with greased plastic and let them rise for 40 minutes. Halfway through the rising time, preheat the oven to 350°F.
At the end of the rise time (the buns won't look very different; that's OK), brush the tops with the reserved egg white beaten with a tablespoon of water. Score or poke the tops of the buns in a decorative pattern.
Bake the buns for 50 to 55 minutes, until the tops are golden brown (check after 35 minutes and tent with foil if needed), and the center measures 195°F when measured with a digital thermometer. Remove them from the oven, tilt them out of the pan, and cool on a rack.
To make the glaze: Whisk together all of the ingredients to make a smooth glaze; drizzle over the tops of the cooled buns.
