Heat the leftover brisket in a covered pot over medium-low heat. Add enough water to keep about ½" of liquid in the bottom of the pot. Stir frequently and add more water a little at a time as necessary. Brisket will be fully reheated in about 15 minutes. Remove from the heat and shred the meat with two forks.
Preheat ½" (about 1 cups) of vegetable oil in a small frying pan to 350°F.
Place a tortilla in the hot oil and cook for 5 seconds. Use tongs to turn it over and cook another 5 seconds. Remove the tortilla from the hot oil and place on paper towels to drain. Repeat with the remaining tortillas.
Preheat 1 ½" (about 3 cups) of vegetable oil in deep pot to 350°F.
Arrange the brisket in a line in just below the center of the tortilla from left to right. Starting at the closest edge, pick up the edge of the tortilla and carefully roll it up and over the brisket. Pull it back to tighten it and and continue to roll up the taquito. Make them tight - A rolled taquito should be ¾" to 1" in diameter. Place a toothpick through the center of the taquito about ½" from the end of the tortilla. Anything less than ½" may cause the tortilla to tear when frying. Repeat with the remain taquitos.
Working in batches, drop 3 or 4 taquitos into the hot oil and cook until golden brown, about 45 seconds. Turn them over and cook another 45 seconds. Remove the taquitos from the oil and drain them vertically over a folded up paper towel inside a tall glass for 30 seconds. This will quickly drain the remaining oil and keep the taquitos crisp.
Arrange the taquitos on a plate and drizzle Mexican crema, or diluted sour cream, over the top. Serve with roasted tomatillo salsa verde.