Preheat oven to 350°.
Using a small pot, bring 2 cups of water to a boil.
Place pearl onions in the boiling water for 3 minutes to make the removal of their skins easier.
Drain cooked onions in a colander and rinse with cold water.
Then, using a paring knife, remove the skins.
In a large skillet, heat butter and olive oil over medium-high heat.
Cook onions and garlic for about 5 minutes or until they begin to turn golden brown.
Reduce the heat to medium, add the sliced mushrooms and green beans, and then cook for another 5 minutes.
Once beans begin to become soft, remove from heat and allow to cool.
In a separate bowl, combine yogurt, flour and pepper.
Stir this mixture into the beans and then transfer to a 2-quart baking dish.
Top with shredded cheese and almond slices, and bake for 35 minutes.