Pat the pork loin dry on all sides, then place on a wire rack set on top of a small rimmed baking sheet.
In a small bowl, combine melted butter, garlic cloves, chopped fresh rosemary, Dijon mustard, fennel seeds, kosher salt, and black pepper. Brush this all over the pork loin, coating it evenly on all sides.
When ready to cook, place the pork loin in a large skillet or baking dish, fat side down. When ready, drizzle with extra virgin olive oil, then place into the oven. Cook.
Carefully place the hot skillet over medium heat. Add chopped shallot, then cook, stirring occasionally, until softened. Increase the heat to medium-high, then whisk in dry white wine. Add chicken stock, then whisk in Dijon mustard.
Add drained butter beans, then cook over medium heat until warm. Turn off the heat, then add unsalted butter. Carefully stir or swirl the pan until the butter has melted, being careful not to break the beans too much. Taste and adjust seasoning as needed.
Cut the pork loin into slices. Spoon some of the butter beans onto each plate, then serve with a couple slices of pork loin on top. Finish with a sprinkle of flaky sea salt, then enjoy!