Preheat the oven to 350 degrees.

Combine feta cheese, sour cream, 1/2 head of roasted garlic, salt, and pepper to taste and mix thoroughly.

Place the baguette slices on a baking sheet and spray the tops with olive oil cooking spray. Cook for 5-7 minutes or until golden brown. Remove from oven and set aside.

Heat 1/2 tbsp olive oil and 1/2 tbsp butter in a large skillet over medium heat. Add onion and saute for 20-25 minutes, stirring often, until lightly caramelized. Remove from pan and set aside.

Re-heat the large skillet over medium-high heat adding the remaining 1/2 tbsp olive oil and 1/2 tbsp butter. Add mushrooms and saute, stirring occasionally, until golden brown, about 5 minutes.

Add the onions back into the pan with the mushrooms and heat through; season with sea salt and freshly cracked pepper, to taste.

Spread the feta mixture evenly onto the crostini then top with a spoonful of mushrooms and onions. Eat & enjoy!