To make the harissa, place all ingredients except lemons and olive oil in a food processor, blitz for 5 minutes until smooth. Transfer to a large bowl, fold in l/4 teaspoon finely grated lemon zest and the juice from the whole lemon and olive oil to taste—the salsa should be very loose and oily. Season with salt.
To make the pickled cucumbers, combine all ingredients in a mixing bowl and stir to combine.
For the yogurt, mix all ingredients together in a bowl.
Make the tortillas: In a stainless steel bowl, combine all dry ingredients. Put the bacon fat or oil in a small bowl and whisk in half the milk. Pour over the dry and gently fold together by hand. Add as much of the remaining warm milk as needed to make a sticky dough. Turn onto a well-floured bench and knead until elastic and well combined. Wrap and chill, allow dough to relax at least one hour.
Divide dough into 12 rounds; roll each piece into a round ball. Let dough relax about 15 minutes. Using a generous amount of flour, roll each ball into a large round. Set tortilla aside, separating each with parchment paper. On a hot grill, flat top, or cast iron pan cook each tortilla until puffy and nicely golden, 1 1/2 to 2 minutes.
For the venison, season the meat generously with salt and pepper. Heat oil in a cast iron pan and sear the meat on all sides until cooked medium rare/rare or desired temperature, 6 to 8 minutes per side for medium rare. Allow the meat to relax and reserve until ready to use. Slice the meat thinly.
To assemble the tacos lay two to three slices of venison on each tortilla. Top with a small amount of pickled cucumbers, a nice dollop of fennel pollen yogurt. Then add a generous amount of chipotle harissa, and finish with baby cilantro.