Trim off an inch or two of fat from the beef add to to the pressure cooker and turn to sauté (or medium high heat if using stove top). Brown the beef on all sides in 2 or 3 batches.
Add remaining Filling ingredients. Close pressure cooker and switch to high pressure for 30 minutes. Let pressure release naturally.
With a slotted spoon, remove the beef and shred. Reserve the cooking liquid. Discard the bay leaf.
Soak corn husks in warm water for at least 15 minutes.
In a medium bowl, combine masa mix, baking powder and salt. Add 3 cups of reserved cooking liquid to make a soft dough.
In another bowl, whip lard or shortening with a beater until fluffy. Beat into the masa dough until smooth.
Tear one or two corn husks into long thin strips for tying (or use kitchen twine) Spread masa mix on the corn husks. Add a tablespoon of beef to the middle. Add a teaspoon of cooking liquid on top of the beef.
Close the husks folding toward the inside. Fold the bottom up and tie with the corn husk strip (or twine) to secure. One side will remain open.
Place tamales open side up on a trivet if large enough or in a steamer basket that will fit in the pressure cooker.
Add 2 cups of hot water to the bottom of the pressure cooker. Pressure cook for 20 minutes on high. Let pressure release naturally.