Remove the stalks from the mushrooms.
Place 50g of butter in a sauté pan and add mushrooms skin-side down.
Season with salt and pepper, cover, and cook gently for 15 to 20 minutes.
Melt the remaining 50g of butter and brush it over the cooked mushrooms.
Mix 50g of breadcrumbs with garlic, chives, and crumbled blue cheese.
Fill each mushroom with the mixture, cover, and cook for 5 to 10 minutes.
Combine garlic and egg yolks in a bowl to begin the aioli.
Add mustard then slowly whisk in the oil until thickened.
Stir in parsley, paprika, lemon juice, salt, and pepper.
Remove mushrooms from the pan and keep them warm.
Fry the remaining 50g of breadcrumbs in the mushroom pan for 5 minutes until crisp.
Sprinkle the fried crumbs over the mushrooms and serve with aioli.