FOR THE CAKE

Preheat oven to 350 degrees.  Line three 9-inch cake pans with wax paper rounds.  Grease and lightly flour rounds and insides of pans and set aside.

1. Add the baking soda to the buttermilk and set aside.
2. In a large bowl, sift together the flour, salt, baking powder, cinnamon, cloves, and allspice and set aside.
3. Add the butter and sugar to the bowl of a stand mixer fitted with the paddle attachment or use a hand mixer.  Mix on high speed for about 1 minute until the sugar is incorporated into the butter and the mixture is smooth and creamy.  Add the eggs, one at a time, mixing well after each addition.  Add the blackberry jam and mix until fully incorporated.
4. Add 1/3 of the dry ingredients, mixing on medium speed until the flour is barely incorporated.  Add 1/2 of the buttermilk and mix to incorporate.  Add the remaining flour and buttermilk alternately, ending with the flour.  Do not overmix.
5. Divide the batter equally between the 3 lined cake pans.  Gently shake pans to level out the batter.  Bake for approximately 30 minutes or until the cakes are golden brown on top and a toothpick inserted in the centers comes out clean.  Allow cakes to cool in pans for 5 minutes.  Invert cakes onto wire racks and remove the wax paper rounds.  Leave cakes on racks until completely cooled.

FOR THE ICING

1. Add the butter, brown sugar, half & half, salt & vanilla to a medium saucepan.  Bring to a boil over medium heat, stirring constantly.  Cook for 2 minutes and remove from heat.  Using a hand mixer, add the powdered sugar one cup at a time, mixing until smooth.  The icing will be on the thin side at first, but as soon as it begins to cool it will quickly become thicker.
2. Place one cake layer on a cake plate and spread 1/3 of the icing over it.  Place a second layer over the icing and spread a second 1/3 of the icing over it.  Place the third layer on top of the icing and spread the remaining 1/3 of the icing over the top.  If the icing begins to get too thick while you’re spreading it, dip your knife in some hot water.  You can also add a tiny bit of warm half & half to the icing to thin it if needed.
3. For best freshness, keep cake refrigerated until an hour or so before serving.