Whisk together flour, arrowroot powder, baking soda and salt.

Cream together shortening, oil and sugar with a handheld or stand mixer. Mix in vanilla and almond extracts and lemon zest.

Whisk together non-dairy milk, apple cider vinegar and sourdough starter, then beat into creamed mixture until combined.

Add dry ingredients and mix until just evenly incorporated

Cut 2 large sheets of parchment paper. Lay one out on a work surface and lightly dust with flour. Turn dough out onto parchment, pat into a rectangle and dust lightly with flour. Cover with second sheet of parchment paper and roll out to 1/4" thickness. Slide dough, still between parchment paper sheets, onto a baking sheet and refrigerate for 15 minutes.

Take dough out of fridge and slide it back onto the work surface. Remove the top sheet of parchment paper. Use a roughly 2" heart shaped cookie cutter to cut out 24 hearts. Rework and roll scraps if needed to get 24 cookies. Use mini heart cutters to cut small heart-shaped windows in 12 of the cookies. These will be the tops of the cookie sandwiches.

Line 2 baking sheets with parchment paper. Transfer cookie cutouts to baking sheets with the help of an offset spatula, 12 per each sheet.

Preheat oven to 350˚F.

While oven preheats, place cookie sheets in the freezer to firm up the dough. This will help the cookies retain their shape during baking. 

Once oven is preheated to 350˚F. Take cookies out of freezer and bake for 12 minutes, switching racks halfway through baking, until they are light golden brown and slightly puffed.

Transfer cookies to cooling racks and cool to room temperature.

Once cookies are cool pair up tops and bottoms. Spread about a teaspoon of jam on each of the bottom cookies. Then place the top cookies over the jam.

It is best to store the sandwich cookies in an container overnight to allow the jam to set and soften the cookies a little. Cookies will keep stored in an airtight container at room temperature for up to 1 week.