This is pretty much Mark's recipe with a few changes: https://norecipes.com/mushroom-doria-rice-casserole/
Ingredients
For the casserole
1 teaspoon butter (I needed less than 1 T to butter the casserole
350 grams cooked rice (1 rice cooker cup)
100 grams Gruyere cheese (or other melting cheese, grated) (I went lighter)
Fried onions (for garnish) (I didn't use them)
For the filling
180 grams green beans - (I went with 150 grams frozen haricots verts, thawed and then cut into smaller pieces - this way I can avoid blanching, etc. Just thaw, chop and use!)
1 tablespoon butter
100 grams chopped onions (I went with a sweet onion and it was amazing!)
120 grams button mushrooms and 100 grams shimeji mushrooms (I went with an 8oz package of baby bellas, cleaned and sliced - delicious!)
1 teaspoon salt (pretty sure I used a lot more through the course of the recipe - season to taste - I also added black pepper along the way ... most of the salt and the pepper was added after the beans were added to the bechamel andit was reducing - just taste and season!)
For the bechamél
1 tablespoon butter (erred on the side of a fat Tablespoon)
25 gramsflour - about 2 ½ tablespoons (I went with a heaping Tablespoon of flour - I try not to second guess recipes but I know how to make roux! It is 1 part fat to 1 part flour! I was ready to add more flour if needed ... but using less flour was perfect)
1 ½ cups milk
Instructions
Butter a 10-inch casserole dish using about a teaspoon of butter. Move the oven rack to the middle position and preheat the oven to 500 degrees F (260 C). (I preheated to 425 so I could also cook a breaded porkchop at the same time! lol Also? 10" is a little big in my opinion! I would use a smaller dish next time so the rice layer is thicker!)
Bring a large pot of salted water to a rolling boil and the whole green beans. (I got to skip this step because I am using thawed haricots verts instead of fresh green beans)
Blanch the beans by bringing the water back up to a full. Drain the beans and rinse them under cold water to chill them enough to handle. (using frozen beans, I got to skip this too ...)
Trim the stem ends off of the beans and chop them up into 1.5-inch lengths. (I did this with the thawed haricots verts - I chose them to replace the fresh beans because they are thin and delicate whole beans ... I would have selecteed frenched green beans otherwise and just thawed them with no need to chop. I know many people make recipes like this with just chopped beans, but I always prefer when the bens are thinner.)
Melt 1 tablespoon of butter in a frying pan over medium heat and sauté the onions, button mushrooms, shimeji mushrooms (or whatever mushrooms you are using - pretty much nay mushroom will work!), and salt until the mushrooms are starting to caramelize (about 6-7 minutes).
Transfer the mushrooms to a bowl and add the remaining tablespoon of butter to the pan along with the flour. (I just pushed the mushrooms to the edge of the pan and put the butter and flour in the middle of the pan. It might feel easier to make the roux with an empty pan and either way will work, but I like not having to remove anything from the pan if it only needs to go right back in!)
Cook the roux until there are no lumps of flour, but don't let it brown. (If you leave the mushrooms and onions in the pan, start mixing the roux in the center but don't worry when inevitably the mushrooms get mixed in - I wound up with everything mixed together and I kept it moving until I could smell the roux was done - since it is not to be browned, you know its done when it starts to smell a little nutty. It will look very dry - its fine!)
Turn down the heat and pour the milk in all at once. Stir the mixture vigorously until there are no lumps of roux remaining.
Turn up the heat to medium and bring the béchamel to a boil to thicken. Add the sauteed mushrooms as well as the green beans to the pan, and stir to distribute evenly. (I just had to add the beans since the mushrooms and onions never left the pan!)
To assemble the Doria, spread an even layer of rice along the bottom of the buttered casserole dish.
Top with the mushroom and green bean béchamel.
Cover with an even layer of shredded cheese.
Put the Doria in the oven and bake until the sauce is bubbly and the cheese has browned on top, about 15-20 minutes.(Since I had a lower oven temperature, I went with 23 minutes at 425*F and it was PERFECT!!!