Preheat oven to 350F and set an oven rack at the middle shelf of the oven.
In a medium bowl sift the flour, baking powder, baking soda, and spices. Set aside.
Measure the sour cream and fig jam (or paste) in a medium bowl and mix to combine. Set aside.
In a bowl of a standing mixer fitted with the paddle attachment beat butter, brown sugar, sugar, and molasses on medium-high for 4-5 minutes. Scrape the sides and bottom of the bowl 2-3 times.
Slowly drizzle the oil and mix for additional 3-4 minutes. Until light and fluffy.
Add the eggs, one at a time waiting for each egg to fully incorporate before adding the next.
Scrape the sides and bottom of the bowl then add the flour mix in three additions alternating with the sour cream mix.
Right after adding the third portion of the flour, turn mixer off and complete blending with a rubber spatula.
Fold in chopped figs.
Pour batter on top of the crust and fig paste layers and bake for 40-45 minutes or until a toothpick comes out clean from the center of the cake.
Once the cake has cooled remove from pan, place on a serving dish and top with walnuts.