Preheat your oven to 350F/ 180C and grease two 8-inch cake pans, set aside.
In a large bowl whisk together the flour, baking powder, baking soda, and salt.
In another large bowl with a handheld mixer or your stand mixer fitted with the paddle attachment beat the butter for 2 minutes, add the oil, and mix for an additional minute.
Add the sugar and beat for 2-3 minutes, until light and fluffy. Add the eggs.
In a small cup or bowl add the coffee granulates and hot water- stir until coffee granulates have disappeared. Add to the wet ingredients.
Gently fold in half of the flour mixture, then half of the buttermilk then repeat with remaining ingredients. Pour into prepared pan and bake for 20-25 minutes, or until you stick a toothpick in the center and only moist crumbs come out, no wet batter. Let cool on a wire rack for 20 minutes before inverting to cool completely.
Place one cake layer on a cake board or serving plate, spread about 4oz (1/2 Cup) of frosting on the cake, making the edges higher to create a frosting dam for the apricot jam.
Spread jam within that frosting dam and place the remaining cake layer on the top, bottom face up- this helps create a flat top.
Spread frosting on the top layer and decorate with roasted walnuts.