In your pressure cooker, hit the Brown button to heat the bottom of your pan.
Add the olive oil and shallots, garlic, and mushrooms, and cook until shallots are softened and mushrooms are softened and browned.
Season with salt.
Add the butter, and melt.
Add flour, and stir well to combine, cooking for 1 minute.
Slowly add the milk and broth, stirring constantly.
Let the cream sauce cook for 5-6 minutes, until slightly thickened.
Add the green beans and stir well to combine.
Close and secure lid.
Cook on high for 8 minutes, letting pressure naturally release once it's finished cooking.
Preheat oven to 400 degrees F.
Place fried onions on a baking sheet.
Bake in preheated oven for 5-6 minutes, until golden.
Top green bean casserole with warmed fried onions.
Serve and enjoy!