Preheat oven to 425°.
Combine mushrooms and fennel seeds in a food processor or spice grinder; process until finely ground. Combine salt and garlic to make a paste. Rub pork with garlic paste; sprinkle with mushroom mixture.
Heat oil in a large cast-iron skillet over medium-high heat. Add pork; cook 5 minutes or until browned, turning occasionally.
Place pan in oven; bake at 425° for 15 minutes or until a thermometer registers 160° (medium) or desired degree of doneness. Transfer the pork to a jelly roll pan, and let stand 10 minutes.
Place pork on a cutting board, reserving juices in jelly roll pan. Combine the reserved juices and broth in cast-iron skillet; bring to a boil, scraping pan to loosen browned bits. Drizzle the broth mixture over pork.