- Preheat the oven to 350F. 
- Sift the flour and set it aside. 
- Chop black walnuts if necessary. 
- Place butter in a large mixing bowl. 
- Add lard or shortening. 
- Use a mixer to blend butter and shortening for 3 minutes. 
- Gradually mix in light brown sugar until smooth. 
- Add granulated sugar gradually, mixing until light and fluffy. 
- Add eggs one at a time, mixing until combined; scrape the bowl as needed. 
- Alternate adding flour and milk, starting and ending with flour. 
- Incorporate butter nut flavoring, mixing until combined. 
- Add the walnut pieces. 
- Gently fold the nuts into the mixture by hand until combined. 
- Grease and flour three 8-inch cake pans. 
- Divide the batter among the three pans. 
- Bake at 350F for 20-30 minutes or until a wooden toothpick comes out clean. 
- Remove from the oven and place the pans on a wire rack to cool for 10 minutes. 
- Remove the layers from the pans and transfer them to a wire rack to cool completely.