Cook shells in a large pot of boiling salted water for about 9 minutes (slightly undercooked). Drain and rinse with cold water.
Meanwhile, heat oil in a large skillet. Add mushrooms and cook with black pepper and 1 tsp. salt, stirring occasionally. Reduce heat to medium, add wine, and cook stirring, until reduced by half. Add spinach and cook, stirring occasionally, until spinach is completely wilted. Transfer to a large bowl.
Cook garlic with olive oil in a skillet over medium-high heat, stirring occasionally. Add tomato sauce and pepper and bring to a simmer over low heat. Cook, stirring occasionally, until warmed through.
Add half of the Violife Grated to the mushroom mixture and stir to combine. Spoon about 2 tbsp of the mixture into each shell. Add the tomato sauce in a baking tray and submerge stuffed shells within. Sprinkle with the other half of the Violife Grated. Place in the oven at 160°C for 10-15 minutes.