In a large bowl, whisk together whole wheat flour, all-purpose flour, sugar, baking powder, salt, and baking soda.

Cut in butter using a pastry blender until the mixture resembles coarse crumbs.

Stir in raisins.

Preheat oven to 350°F (175°C).

Lightly beat the eggs, then remove 1 tablespoon of the beaten egg and set aside for brushing.

Add buttermilk and the remaining beaten egg to the flour mixture and stir until just moistened. The dough will be sticky.

Turn the dough out onto a well-floured surface.

Knead the dough about 10 times to mix thoroughly.

Shape the dough into a ball and place it in a greased 2-quart round casserole dish.

Using a sharp knife, cut a 4-inch cross about 1/4 inch deep in the center of the dough ball.

Brush the dough with the reserved egg.

Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean.

Let the bread cool in the casserole dish on a wire rack for 10 minutes.

Remove the bread from the casserole dish and let it cool completely on the rack for 30 minutes before slicing.

Serve warm or cold.