Apple Walnut Tea Cake

Preheat the oven to 350u0b0 F. Grease a 9 x 5-inch loaf pan (or two 5 x 3-inch loaf pans) and line the bottom(s) with parchment paper. Spread the walnuts on a baking sheet and toast until golden brown and fragrant, about 10 minutes. Remove from the oven and let cool completely, then coarsely chop.
In a large bowl, mix together the leaven, egg, kefir cream, and grated apple. In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, cinnamon, salt, nutmeg, cloves, and ginger. Add the olive oil to the dry ingredients and, using a bench knife or pastry cutter, cut the oil into the flour until well distributed. Stir in the walnuts, then add the flour and oil mixture to the wet ingredients and stir well to combine.
Transfer the batter to the prepared pan(s). Bake for 60 to 70 minutes (30 to 40 minutes for miniature loaves), or until the internal temperature of the cake reaches 200u0b0 F. Let cool in the pans for 30 minutes, then use a knife to loosen the cake from the pan(s) by slicing around the edges. Unmold onto a wire rack, and let cool completely. The cake will keep at room temperature, wrapped, for up to 3 days.