How to Make It
In a medium bowl, whisk 3/4 cup of the stock and 1/4 cup of the vinegar with the coconut milk, mirin, fish sauce, curry powder, peanut butter and mustard. Transfer to a large, resealable plastic bag. Add the lamb chops and turn to coat completely. Seal the bag and refrigerate overnight.
Roast the red pepper over a gas flame or under a broiler, turning, until blackened all over. Transfer the pepper to a small bowl, cover with plastic wrap and let cool. Peel the pepper and discard the core and seed. Transfer the pepper to a blender. Add the remaining 1 tablespoon of stock and 1/2 tablespoon of rice vinegar and puree until smooth. With the machine on, add the oil and puree until creamy and smooth. Season the sauce with salt.
In a small bowl, toss the cucumber with a pinch of salt and let stand until softened slightly, about 5 minutes.
Light a grill or preheat a grill pan. Drain the lamb chops and grill over high heat, turning once, until charred and medium-rare, about 7 minutes. Transfer the chops to plates and serve with the red pepper sauce and cucumbers.