Add the water, sourdough discard, cane sugar, olive oil, yeast, and salt to the bowl of a stand mixer. Turn the mixer on and gradually add both flours, mixing until a dough forms. Let the dough rest for about 10 minutes so the freshly milled flour can absorb the water.
Knead the dough for about 15 minutes, until it becomes smooth and elastic. Cover the bowl and let the dough rise for 45 minutes to an hour, or until doubled in size.
Once dough has doubled, divide the dough into two equal portions. Shape each portion into a ball, creating tension across the surface. Place each dough ball in a lightly oiled bowl, covered. Refrigerate the dough for 30 minutes to 1 hour before shaping. For more developed flavor, refrigerate it overnight and reduce the yeast to ½ teaspoon.
Preheat the oven to 500°F, or 260°C, with a cast iron pizza pan or pizza stone inside.
Sprinkle a pizza peel with semolina flour. For easier transferring, place a sheet of parchment paper on the peel and sprinkle the parchment with semolina. Place one dough ball in the center and gently stretch it outward, about 12 inches wide, taking care not to flatten all the air bubbles around the edges.
Transfer the dough to the hot pizza pan or stone. Parbake for 5 minutes, until the crust is set and almost fully baked. (For freezer pizza, stop here, let it cool down, add your toppings and flash freeze before wrapping it up for the freezer.)
Remove the crust from the oven and add the sauce, cheese, and desired toppings. Return it to the oven and bake for about 10 more minutes, until the crust is fully cooked and the cheese is melted and browned. Repeat with the remaining dough ball.