Line 2 cookie sheets with parchment paper and set aside. You will have to bake in batches.
Using a stand mixer with a paddle attachment, or a hand mixer, cream together the butter and the sugar. Beat in the egg completely, then add the coffee or sour milk and the vanilla. Mix until combined.
Whisk together the dry ingredients in a medium-sized bowl until combined.
Add the dry ingredients to the wet mixture, then on low-speed beat until the ingredients are combined completely.
Stir in the raisins and dates by hand until mixed throughout the batter.
Drop by tablespoonful onto a cookie sheet. If you want them flatter, slightly press them down.
Bake in the oven until lightly browned and the edges are set. Remove and cool on the baking sheets completely.
Notes
Coffee gives these a darker flavor and is my favorite way to make them instead of the sour milk
These are best baked until the edges are browned and the middle just set. Overbaking them will make them hard.
Storing them in a closed container between sheets of parchment makes sure they retain their soft texture.