Heat the oven to 350°F and cover two cookie sheets with parchment paper. The lined sheets provide a surface where the delicate cakes can bake and cool without transferring them.
Combine the almond flour, granular Swerve, cocoa, baking powder, and baking soda with a whisk, then pass the mixture through a sifter into another bowl. The dry mixture should look evenly blended, without visible cocoa or flour clumps.
Whisk the eggs, milk, olive oil, vanilla, and vinegar into the sifted mixture until uniformly combined. Expect a thick batter that holds a mound when scooped.
Deposit half-scoop portions with an ice cream scoop onto the prepared sheets. Keeping the portions consistent helps the finished sandwich halves match.
Use a toothpick to tidy each mound into a circle about 2.5 to 3 inches across, leaving generous gaps. The batter will spread during baking, so the rounds need room around their edges.
Portion the batter into 15 rounds total. This provides pairs for seven pies and one spare round if a cake breaks during handling.
Bake the sheets on the top and bottom oven racks for 12 to 14 minutes, then leave the rounds on their sheets until completely cool. The cakes feel delicate while warm and become firmer as they cool.
Use the optional 15-minute freezer cooling shortcut by placing the cookie sheets in the freezer. Handle the rounds only after they have cooled completely and feel firm enough to lift.
Beat the softened cream cheese and butter with a hand mixer, blend in the milk and vanilla, then sift in the confectioners Swerve and salt and beat again. The finished filling should look creamy and evenly blended.
Chill the filling if it needs thickening, then transfer it to a piping bag or a large zip-top bag with a corner snipped off, or reserve it for spreading with a knife. A thicker filling holds its shape more readily between the cakes.
Turn seven cooled rounds flat-side up, pipe or spread filling over them, and cap each with a matching round. The flat undersides create level surfaces for the filling and support the domed tops.
Refrigerate leftover assembled pies in an airtight container. The closed container helps protect the cakes from drying out.