Crock-Pot Cuban Style Flank Steak

This dish takes a really long time to cook.  I split the cooking into two separate days.  I made this dish specifically for my stepdaughter & her boyfriend.  They love beef & they love Cuban food.  They actually knew this dish when they ate it.  They were really excited about it.  My stepdaughter's boyfriend's family is from Puerto Rico & they travel to Puerto Rico at least once a year.  In fact, they are leaving for Puerto Rico TONIGHT.  I did taste it, & it was quite good I have to say.  My stepson said it was "just ok".

Crock-Pot Cuban Style Flank Steak

First Cooking:
1 flank steak, approximately 2 lbs
1 large onion, thinly sliced
6 cloves garlic, minced
1 teaspoon dried oregano leaves
1/2 teaspoon salt
8 cracked black peppercorns
1 bay leaf
2 Tablespoons freshly squeezed lemon juice
water or beef stock

Second Cooking:
2 Tablespoons oil
8 ounces mushrooms, thinly sliced (I left these out cuz my stepkids HATE mushrooms)
2 onions, finely chopped
1 teaspoon chili powder
1 teaspoon dried oregano leaves
1 hot chili pepper, minced, optional
1 teaspoon salt
1/2 teaspoon cracked black peppercorns
1 Tablespoon all purpose flour
1 each red & green bell pepper, roasted, peeled, & cut into strips
2 Cups shredded Monterey Jack cheese, optional
Hot cooked rice or tortillas

First cooking:
*place steak in slow cooker
*spread onion slices evenly over meat
*sprinkle garlic, oregano, salt, peppercorns, & bay leaf over onions
*drizzle lemon juice over seasonings & add water to cover
*cover & cook on low for 8-10 hours or on high for 4-5 hours, until meat is tender & shreds easily
*allow meat to cool in cooking liquid (if not proceeding to second cooking immediately, cover & refrigerate meat & liquid until ready for second cooking)

Second cooking:
*strain & reserve cooking liquid
*using two forks, tear meat into shreds & transfer to slow cooker stoneware
*in a skillet heat 1 Tablespoon oil, add mushrooms & cook until they lose their liquid & then transfer to slow cooker
*add remaining oil & onions & cook until softened
*add chili powder, oregano, chili pepper (if using) salt, & peppercorns & cook for 1 minute
*sprinkle flour over mixture & cook for 1 minute; add 1/2 cup reserved cooking liquid & cook, stirring, until thickened; pour over beef & mushrooms & stir to combine
*lay pepper strips over top of mixture
*cover & cook on low for 4 hours or on high for 2 hours, until mixture is hot & bubbly; add cheese if using
*cover & cook on high for 10 minutes, until cheese is melted; serve over hot cooked rice or with tortillas