Mix the flours and salt. Add the yeast to the water. When the yeast is fully dissolved, make a thick dough by pouring flour mixture into water and blending well. The ratio of flour to water depends on the nature of the flours. This ratio of 1:2 by volume works well in Finland with Finnish flours. Where flours contain more gluten you should use slightly less water.
Set aside about 4 T of dough to be used later. Roll out the remaining dough into a circular shape about 3/4 inch thick.
Finish with the second half of the pork.
Preheat oven to 500 degrees F. Lift the edges of the dough all around the filling and glue together with a little water so that you have the filling surrounded from all directions with about 3/4-inch-thick dough. Put upside down (the seam downwards) on a baking sheet and let it rise about half an hour at room temperature.
Put the kalakukko in a 500 degree F. oven for long enough to brown the dough, which will seal it against moisture. Then lower the temperature to about 250 degrees F. and let it bake for 4 to 7 hours depending on the size of the fish (bigger fish need more cooking time). You can brush some melted butter over the top of the dough just after lowering the temperature; this will give it a prettier appearance. If it starts to leak while baking, fill holes with the dough which was set aside.
Serve hot or cold.
NOTES:* Rye bread pie with fish and pork filling - This is an ancient national food prepared and eaten in Savo (eastern Finland).
Make sure you use un-smoked pork.
Difficulty: moderate (some skill with dough is required).
Precision: Careful measurement not necessary, but the consistency of the dough (which will depend on the nature of your flours) is important. If the dough is either too soft or too hard, the kalakukko will leak.