Preheat oven to 350°F. Grease a 13x9 inch pan or 12x8 inch pan with cooking spray.
Place the dates and baking soda in a heat-proof bowl. Pour the boiling water over the top and set aside for 15 minutes to cool.
In a large bowl, whisk together the flour, cocoa powder, and salt.
In the bowl of a stand mixer, beat the butter and sugar until light and fluffy. Add the eggs, vanilla, and orange zest, and beat until combined. Scrape down the sides of the bowl.
Add half of the flour mixture, and mix until combined. Add half of the date/water mixture, and mix. Repeat with the remaining flour mixture and remaining date/water mixture.
Stir in half of the chocolate chips. Pour the batter into the prepared pan. Sprinkle with the remaining chocolate chips and the walnuts.
Bake for 35–40 minutes, or until a toothpick comes out clean.
Notes
I like serving the cake with a dollop of whipped cream or Cool Whip on top.Variations: you can omit the orange zest, if you'd like. You can also substitute pecans for the walnuts. Grandma used shortening instead of butter—do what you prefer! Store the cake tightly covered at room temperature for up to 5 days. You can also freeze the cake, tightly wrapped, for up to 3 months.