Preheat oven to 325.
In the bowl of an electric mixer fitted with a paddle, combine 4 cups flour, raisins, baking powder, salt, and baking soda. Mix on low speed for 2 minutes.
In a stainless steel bowl, gently whisk the buttermilk and vegetable oil. Gradually add the buttermilk mixture to the dry ingredients while mixing on low speed until the dough forms a ball, 30-40 seconds. Scrape the dough away from the paddle and turn the dough ball over. Mix on low speed for another 30 seconds.
Transfer the dough to a floured surface. Knead vigorously until smooth, about 2 minutes. Form the dough into round loaf. Pinch a small handful of dough & gently twist, careful not to tear the dough from the loaf. Place dough, pinched side down, on a baking sheet lined with parchment paper.
Whisk the egg yolk with 1 tablespoon water, then lightly brush the mixture over the top of the loaf. Score the loaf by cutting a 1/4’’ deep ‘X’ into the top.
Bake the loaf in the preheated oven for 50 to 55 minutes. The bread is done if a hollow sound is heard when the bottom is tapped with your finger.
Allow the bread to cool to room temperature before slicing.
