Preheat your oven to 400°F (200°C).

In a large frying pan, heat a tablespoon of olive oil over medium-high heat. Add sliced mushrooms for garnish and sauté until golden, about 2-3 minutes.

Remove sausage casing, crumble into the pan, and cook over medium heat for 3-4 minutes until browned.

Add minced garlic, chopped mushrooms, salt, and black pepper; cook for another 3-4 minutes until mushrooms soften.

Toss in fresh baby spinach and cook until wilted, about 3-5 minutes. Remove from heat and let cool slightly.

In a mixing bowl, combine softened cream cheese, shredded mozzarella, grated Parmesan, and sour cream. Mix until smooth.

Fold in the cooled mushroom and sausage mixture into the cheese blend until evenly distributed.

Pour the dip mixture into an oven-safe baking dish, smoothing the top. Sprinkle sautéed mushrooms on top for garnish.

Cover with foil and bake for 10-12 minutes until bubbling. Remove foil and bake an additional 2-3 minutes for a golden top.

Let it cool slightly before serving with toasted baguette slices, crackers, or veggie sticks.