Step 1

Pound steaks very thin, about 1/8-inch thick, using the flat side of a mallet. Spread 1 tablespoon mustard over each; sprinkle with salt and black pepper.

Step 2

Center 1 bacon slice on each steak. Sprinkle 1 tablespoon onion on top; reserve remaining onion. Place 1 pickle spear at the end of each steak; roll up, tucking edges in. Secure rolls with kitchen string.

Step 3

Heat oil and butter in a Dutch oven over medium-low heat. Place rolls in the Dutch oven; fry until very dark on all sides, 20 to 30 minutes. Transfer to a plate.

Step 4

Place remaining onion in Dutch oven over medium heat. Cook and stir, scraping bits from the bottom, until onions are translucent, about 5 minutes. Add 1/2 teaspoon salt; stir. Add 1/4 cup boiling water; scrape the bottom again.

Step 5

Return rolls to the Dutch oven. Add additional boiling water to just cover rolls; place lid on Dutch oven. Reduce heat to low; simmer until meat is very tender, about 90 minutes. Check from time to time, adding more boiling water if needed. Season with salt and pepper.

Step 6

Transfer rolls to a plate; keep warm. Combine ice-cold water and flour in a small container with a lid; shake to blend. Add mixture slowly to the simmering juices; stir until gravy is thickened, about 5 minutes.

Step 7

Arrange rolls on a serving platter; cover with gravy.