Preheat oven to 450 degrees F. Line a cookie sheet with foil and spray with nonstick spray.
Wash green beans and trim the ends. Cut beans in half on an angle.
Place green beans and mushrooms in a large bowl. Sprinkle with olive oil, salt, pepper and Panko bread crumbs. Use a spoon to stir the beans and coat them really well with the olive oil. Pour the beans onto the cookie sheet. Spread out as much as possible.
Place cookie sheet in oven and roast for 20 minutes. Check for doneness, if needed cook a few minutes longer.
While beans are cooking, prepare the Hollandaise sauce. Whisk egg yolks, water and lemon juice in small saucepan until blended. Cook over very low heat, stirring constantly, until mixture bubbles at the edges.
Stir in butter, 1 piece at a time, until butter is melted and until sauce is thickened. Remove from heat as soon as sauce is thickened.
Stir in salt, paprika and pepper.
Spread the cooked green beans onto a platter. Drizzle hollandaise sauce over the top of the beans and serve immediately.