Heat a heavy pan on medium high until very hot.
Add butter, swirl around pan, and let melt.
When butter is foamy and melted, add chicken thighs.
Very lightly salt chicken thighs (ONE pinch for all things - don't overdo it!)
Cook chicken thighs 5 minutes on each side, until lovely golden brown.
When chicken thighs are well browned, remove from pan - do not drain pan grease.
Add garlic to pan, stir well.
Add mushrooms to pan, stirring occasionally to keep mushrooms and garlic from burning.
Add second half of butter to pan, let melt.
Let garlic and mushrooms brown - about 4-6 minutes. Do not let garlic burn, reduce heat if needed.
Add red pepper flakes (add slowly according to your taste) and cilantro when chicken and mushrooms are lovely golden browned.
Add stock, lemon juice, and cheese.
Stir well, being sure to scrape up any browned bits from bottom of pan.
Bring to a boil, let reduce and thicken slightly for 2 minutes.
Add chicken thighs back to pan, let sauce reduce another 5-8 minutes, flipping chicken occasionally, until thick and chicken thighs are 165 internal temp.