Using a serrated bread knife in a gentle sawing motion, trim and discard crusts from bread slices, creating 4 (3-inch) squares. Cut bread squares diagonally into 4 equal triangles, creating 16 triangles.
Using a bread triangle as a pattern, cut 8 triangles from cheese slices.
Create a triangle of pork by folding a pork slice in half and then in half again. Using a sharp knife, trim excess to fit bread triangle, if necessary.
Using a sharp knife, cut very thin vertical slices from apple. Using bread triangle as a pattern, cut 8 triangles from apple slices.
In a small bowl, stir together mustard and mayonnaise until combined.
Spread a thin layer of mustard mixture onto bread triangles. On mustard side of each of 8 bread triangles, arrange kale, and top with a cheese triangle, a piece of folded pork, and an apple triangle. Cover each with another bread triangle, mustard side down.
Serve immediately, or cover with damp paper towels, place in an airtight container, and refrigerate until ready to serve, up to 1 hour.
Recipe by TeaTime Magazine at https://teatimemagazine.com/golden-apple-pork-tea-sandwiches-recipe/