Dough: Heat the butter and milk in a small saucepan, or in the microwave, till the butter has melted. Put the sugar, coriander and salt in a medium-sized bowl, and pour the hot milk over them, stirring to combine and to dissolve the malt or sugar. Set aside to cool to lukewarm.
Add the instant yeast and flour to the milk mixture and stir to form a shaggy mass. Set this rough dough aside for 30 minutes.
Knead the dough until it's smooth -- in a bread machine set on the dough cycle, about 2 minutes in a food processor, 6 to 8 minutes by electric stand mixer, or 8 to 10 minutes by hand. Put the dough in a greased bowl, turn it over to coat the entire surface, and cover the bowl. Let the dough rise for 1 to 1 1/2 hours, or until it increases in size by at least one-third.
Filling: If you have a food processor, use it -- it's ideal for this filling. Cube the hard cheese, add the soft cheese, and process until well-mixed but some chunks remain. Add the eggs, flour and seasonings, and pulse just to mix thoroughly. Refrigerate until ready to use.
If you don't have a food processor, grate the hard cheese, and beat in the soft cheese and eggs. Continue beating, adding the flour and seasonings. Refrigerate until ready to use.
Shaping and Baking: After the dough has risen, turn it out onto a lightly floured surface. Divide the dough in half (you'll be making two loaves), and cut a small (1-ounce) piece of dough off of each half. Round all four pieces of dough into balls, and let them rest, covered, for 15 minutes.
Roll each large ball into a 10- to 12-inch circle. Place one circle into a lightly greased small pie tin, 8- or 9-inch round cake pan, or onto a lightly greased or parchment-lined baking sheet. Dollop half of the cheese mixture into the middle of the circle, and pull the dough up around the cheese, folding and pinching it, and "pleating" it into a topknot. Leave a small hole in the very center of the knot, and place the small ball in this hole. Repeat with the remaining dough and filling. Cover the loaves and let them rise for 45 minutes or longer -- they'll look puffy, but not doubled in size. If the pleats have opened, pinch them shut.
Bake the loaves in a preheated 375°F oven for 15 minutes, then lower the temperature to 350°F and bake for another 20 to 25 minutes. When finished, the loaves will be golden brown, and the middle should feel set. Tent the loaves with aluminum foil after 15 minutes if they seem to be browning too quickly. Remove the loaves from the oven, and allow them to cool for at least 15 minutes before slicing. Slice the bread into wedges, and serve it warm, or at room temperature.
*Heat milk until small bubbles form around the edge, and the occasional wisp of steam is evident.
**Cheese varies greatly in salt content, so taste before adding salt.