MAKES 16 SMALL BARS  Reprinted with permission from Cookies are Magic by Maida Heatter, copyright © 2020. Published by Voracious, an imprint of Little, Brown Books.

For the oatmeal base:
Adjust a rack one-third up from the bottom of the oven and preheat oven to 350 degrees. Line an 8‑inch square cake pan with foil as follows: Turn the pan over, place a 12‑ inch square of foil shiny side down over the pan, and press down on the sides and corners to shape the foil. Remove the foil, turn the pan over again, place the foil in the pan, and press it gently into place. To butter the foil, place a piece of butter in the pan and place it in the oven to melt; then spread it with a pastry brush or crumpled wax paper over the bottom and sides of the pan. Set the pan aside.

Sift together the flour, salt and cinnamon and set aside.
In the small bowl of an electric mixer, beat the butter until soft, then beat in the brown sugar. On low speed, add the sifted dry ingredients, the nuts and the rolled oats. When well mixed, remove and reserve 1 cup of the mixture.

Turn the remaining mixture into the prepared pan. With your fingertips, spread it evenly over the bottom of the pan and then press firmly to make a compact layer. Bake for 15 minutes

For the cream cheese layer:
Combine the zest and juice and set aside. In the small bowl of an electric mixer, beat the cheese until it is soft. Beat in the granulated sugar and then the egg and sour cream. When smooth, remove from the mixer and stir in the zest and juice.

Pour the mixture over the baked bottom crust (which may still be hot). Smooth the top. Now, with your fingertips, sprinkle the reserved oat mixture as evenly as you can to cover the cheese mixture completely (or almost completely). Then, with your fingertips, press the oat mixture slightly into the cheese mixture so that none of it remains loose and also to smooth the top. Bake for 25 minutes.

Set aside to cool completely.

Place the cooled cake in the freezer for about an hour. Then cover the top of the pan with a piece of foil and fold down the sides. Cover the foil with a board or a cookie sheet, turn the pan and the board or cookie sheet over, and remove the pan.

Peel off the foil lining, cover the cake with a board or cookie sheet, and turn over again. Remove the remaining foil (it was put there only to catch any loose bits of topping that might fly around when the pan is turned over).

Now, to cut the cake:
Use a strong, sharp knife. If the cheese mixture sticks to the blade, hold the blade under very hot running water before making each cut (cut with the hot, wet blade). If the cheese mixture squashes out even a bit, place the cake in the freezer again for 10 to 20 minutes (or as necessary) until it is firm enough.

Cut into quarters and then cut each quarter into 4 pieces. Cover and refrigerate until serving time. These may be frozen; if so, thaw in the refrigerator for an hour or two, or longer.