Mix sourdough discard, warm whole milk, instant yeast, granulated sugar, melted butter, bread flour, and kosher salt together.
Hand knead until smooth (might take 10+ minutes with the bread flour - don't add milk, trust the process; if it's tough, let it rest for a few minutes then come back to it).
Roll out into a rectangle (avoid using flour if you can, you should be able to knead it until it's just tacky but not sticky).
Mix together softened butter, Dijon mustard, garlic powder, onion powder, and cracked black pepper.
Spread the butter mixture over the dough.
Top with sharp cheddar, diced jalapeños, and chopped green onions.
Roll tightly, slice into rolls, and place in a buttered 12" cast iron skillet.
Bake at 350°F until golden and the centers are cooked through (about 30 minutes, then optionally put under the broiler for a minute or two to add color).
Brush immediately with melted butter, garlic confit oil, chopped parsley, and chopped chives.
Top with fresh jalapeño slices.
