Add the olive oil to a skillet over medium high heat.
Saute the diced onions for 2-3 minutes until translucent.
Add in minced garlic and saute for 1 minute untl fragrant.
Turn off the heat and stir in milk and parmesan cheese.
Transfer this mixture to a blender or food processor and slowly add in the ¼ cup olive oil blend until smooth. Set aside.
In the same pan over medium high heat, add another tablespoon of olive oil.
Add the mushrooms and cook for 2-3 minutes untl they begin to release some of the moisture.
Stir in thyme, salt, pepper, and the balsamic vinegar.
Continue cooking the mushrooms until they reduced by half. About 10-15 minutes.
While those cook, slice the baguette and drizzle with olive oil.
Broil the slices of baguette for 1-2 minutes until toasted and brown.
Once the bread is done, spread the creamy onion puree on each slice.
Top with the mushrooms and enjoy!