To start the chicken, just cover with water and boil until cooked through. Remove chicken. Let cool and shred with knife and fork. I like to keep the water from the chicken in a mason jar with a lemon wedge, salt, and pepper.
Then in the same pan after the water has been removed, put the olive oil, garlic, and onions. Cook for a minute, then add chicken, wine, and spinach.
Cook until the spinach is heated thoroughly. Then lower heat to low and cover. Stirring occasionally.
To start sauce, on a lower heat whisk egg yolks. Then add butter. Whisk until totally incorporated.
Raise heat to medium while still whisking. Add wine and mustard. Whisk, whisk, whisk.
If you would like to add cheese, now would be the time to do it. Whisk until melt. It should be kind of thick now.
Add cream and beat until a thinned, even sauce. Now add your oregano. Optionally you may want to add a little cayenne for heat, but I usually do not.
I like to serve this with vegetable pasta tossed in olive oil and fresh herbs. Just one scoop of spinach mix and a spoonful of hollandaise. Enjoy and have seconds!