Activate the Yeast: In a small bowl, stir together the warm water, yeast, and sugar until dissolved.
Let the mixture stand for about 5 minutes, or until it becomes foamy.
Make the Dough: In a food processor, pulse the spelt flour and salt to combine. With the machine running, pour the foamy yeast mixture through the feed tube.
Once the mixture is crumbly, drizzle in 2 tablespoons (30 ml / 1 fl oz) of olive oil and process just until the dough forms a ball. If the dough is too sticky, add 1 to 2 more tablespoons of flour.
Let it Rise: Turn the dough out onto a lightly floured surface and knead it briefly.
Place it in a bowl, cover with plastic wrap, and let it rise in a warm spot for 45 minutes.
Prepare Toppings & Oven: While the dough rises, preheat your oven to 450°F / 230°C.
Heat the remaining ½ tablespoon of olive oil in a skillet over medium-high heat.
Add the sliced mushrooms and sauté for 3 minutes until tender. Use a slotted spoon to transfer them to a paper towel-lined plate.
Shape and Assemble: Once risen, punch down the dough and knead it a few times. On a floured surface, use a rolling pin to roll the dough into a 12-inch circle. Carefully transfer the dough to a pizza pan or baking sheet.
Bake to Perfection: Spread the tomato sauce evenly over the dough, leaving a small border.
Sprinkle with the shredded mozzarella, then distribute the sautéed mushrooms on top.
Bake on the lowest oven rack for 20 to 25 minutes, until the cheese is bubbly and the crust is golden brown.
