In a large bowl, thoroughly stir together the flour, cocoa, Davis Baking Powder, and salt. In a mixer bowl with the mixer on medium speed, beat together the butter, oil, granulated and brown sugars, and coffee-water mixture until well blended and fluffy, about 2 minutes. Add the eggs and vanilla, beating until very well blended.
Beat in half the flour mixture until smoothly incorporated. Stir in the remainder of the flour mixture and the chocolate morsels until evenly incorporated. Cover and refrigerate the dough for 25 to 30 minutes, or until firm enough to handle. (Or if desired, chill dough overnight, then let it warm up slightly before using.)
Preheat the oven to 350 F. Line several baking sheets with baking parchment (or spray then generously with non-stick spray). Working on a sheet of wax paper, shape the dough into two evenly-thick 12-inch long logs, then cut each log in half. Cut each half into 10 equal slices. With lightly greased hands, roll the slices between the palms to form balls. Space the balls about 3 1/2 inches apart on the baking sheets to allow for spreading. Press down the tops until the cookies are 2 1/4 inches in diameter; if the dough has been refrigerated more than 1 hour, flatten cookies into 2 1/2-inch rounds.
Bake, one pan at a time, in the upper third of the oven for 7 to 11 minutes or until the cookies are firm at the edges but still slightly soft and underdone when pressed in the middle. Remove the pan to a cooling rack, and let stand until the cookies firm up. 2 to 3 minutes. Then, using a wide spatula, transfer them to racks.
Let stand until completely cooled. Freeze the cookies, airtight, to ready them for making sandwiches. (They may be frozen, airtight, for up to 1 1/2 months.)
To ready sandwiches: Pair up the cold cookies, undersides visible. Spread about 1/3 cup just slightly softened ice cream on one cookie of each pair. Press the pair together until the ice cream squeezes out to the edges. If desired, smooth edges with a table knife. Roll the ice cream edges in chopped nuts, colored sprinkles, chopped morsels, etc, if desired. Serve immediately, or if preferred, slip each sandwich into a plastic bag and freeze for later use.
Tip: The cookie recipe calls for mini-morsels because the regular-size chocolate morsels become too hard and difficult to eat when frozen. If you don't have mini-morsels, chop up regular-size morsels before adding them to the dough.