Preparación:

1. Bring a large pot of salted water to a boil. Add potatoes, lower heat to medium, and simmer until potatoes are tender, 15 to 20 minutes.
2. When the potatoes are almost finished, heat milk and butter in a small saucepan over low heat until the butter is melted.
3. Drain potatoes and return to the pot. Slowly add warm milk mixture, blending it in with a potato masher or electric mixer until potatoes are smooth and creamy—season with salt and pepper.

Fillet: 

1. Pat dry your fillets and season with salt. 
2. Preheat your cast iron or metal pan on medium heat then add your 4 tablespoons of butter with your 2 fillets. 
3. Baste for 2-3 minutes on each side until fully cooked or reach 135 °F / 57°C . Be sure not to burn the fond (the caramelized bits of garlic and shallot). 
4. Strain out the crispy and golden bits of garlic and shallot then place them on top of the fillet. Set aside.
5. Add to butter in the pan: trimmed green beans, half a squeeze of lemon, pinch of salt, and cook on medium to low heat for 3 minutes or fully cooked but still crunchy. 
6. Plate with mashed potatoes, green beans, fillet, pan drippings, and finely chopped chives. Enjoy!