In a large bowl (either by hand or with an electric mixer), combine the first 6 ingredients. Add in 3 cups of the bread flour, mixing to combine, then add the raisins. Finally, add the final 3 cups of flour 1/2 cup at a time, until a stiff dough is formed (depending on the weather and/or how dry your house is, you may not need all 6 cups of the flour). The dough will still seem fairly sticky, but will pull away from the sides of the bowl.
Cover the bowl with aluminum foil (I suggest greasing the inside of the foil) and leave on the counter to rise overnight.
The next morning, gently punch down the dough and knead on a flour surface about 8-10 times. . If using 9x5-inch loaf pans, divide the dough in half. If using 8x4-inch pans, divide into thirds. Knead each part a few times before shaping placing in greased loaf pans. Brush the top of each loaf with oil and cover with a clean tea towel. Let rise 4-5 hours at room temperature, until loaves are doubled in bulk (if your house is cold, rising could take most of the day).
At the end of the rising time, preheat oven to 350 degrees. Bake for 40-45 minutes, until browned on top.
Turn out of loaf pans and place on a rack to cool completely.
Wrap in foil and store in the refrigerator for up to 1 week or the freezer for up to 2 months.
Notes
It is very important that you use bread flour for this recipe, as the extra gluten in the bread flour is what gives your dough elasticity and keeps your final bread light and chewy.Makes 2 9x5-inch loaves or 3 8x4-inch loaves.