Preheat a small saute pan over med-high heat with 1 tablespoon olive oil; add in onions and garlic; season with salt and pepper.
Cook, stirring frequently, for 3-4 minutes.
Add in the grainy mustard, chicken stock, and cream; bring to a simmer; cook until thick, 2-3 minutes.
Turn the sauce off and reheat it when you’re ready to serve (if it thickens up too much, add a splash more of chicken stock to loosen it up).
Place the bread in a food processor; use the pulse button to break it up, then process and make fine bread crumbs.
In a bowl, combine the mayo, scallions, parsley, hot sauce, red bell peppers, salt, and pepper; gently run you fingers through the crab meat, feeling for any shells or cartilage while trying not to break up the meat too much.
Add the crab meat to the mayonnaise mixture with ¼ of the bread crumbs and gently fold the mixture to combine.
Place the remaining bread crumbs on a plate; divide the crab mixture into 4 equal portions.
Transfer the 4 crab portions to the plate with the bread crumbs and coat each one, gently pressing to adhere the bread crumbs and forming 1- to 1 ½-inch thick cakes.
Preheat a nonstick skillet over medium heat with the remaining olive oil and the butter.
Once the butter melts, add the crab cakes and cook for about 4 minutes on each side or until they are golden brown and heated through.
Divide the sauce between 2 plates, top with the crab cakes, and serve.