1. Preheat oven to 325 degrees. In a small skillet, heat 1 cup oil and 1 teaspoon butter over medium-high heat. Add breadcrumbs and cook, stirring, until golden brown, about 7 minutes. Transfer breadcrumbs to a paper-towel-lined plate to cool. Transfer breadcrumbs to a small bowl; stir in 1 teaspoon ginger, juniper berries, and 1/2 teaspoon salt; set aside.

2. In a small bowl, mix together mustard and plum wine vinegar; let stand 10 minutes. Add remaining 2 tablespoons ginger and rice vinegar and mix until smooth; set aside.

3. Heat 1/4 cup oil and remaining teaspoon butter in a large oven-proof skillet over high heat. Sear the lamb on all sides until it is golden brown, about 4 minutes per side. Remove lamb from the skillet, coat with half of the mustard mixture and breadcrumbs. Return to skillet and transfer to oven and cook for 7 minutes for medium.

4. Meanwhile, heat remaining tablespoon oil in a large skillet over medium-high heat. Add bok choy and chile; season with salt. Cook until tender, about 2 minutes. Remove lamb from oven and serve bok choy and remaining mustard.