Mix together Baking Mix, baking powder, salt and Metamucil in a large bowl. Cut in shortening to resemble cornmeal. Add water slowly, mixing with a fork or hands to make a soft dough. You may not need all the water. This step can also be done in a food processor.
Knead a few minutes on floured surface until smooth and somewhat elastic. Put back in bowl and let rest, covered for 10 minutes or more.
Divide into small balls the size of golf balls (about 60g each) and roll out between 2 sheets of wax paper working from the center out, until you have a 7 to 8 inch tortilla a little less than 1/4 inch thick, or place dough ball into a tortilla press.
Transfer the tortilla to a hot, dry skillet or griddle. Let it cook for about 30 seconds until the surface begins to blister and lightly brown. Turn the tortilla over and cook the other side for an additional 30 seconds.
Stack cooked tortillas in a napkin lined basket or plate and cover with aluminum foil.
TIP: Roll out the dough on a floured surface or between wax paper and use the rim of a tupperware bowl as a ""cookie cutter"". Makes perfect rounds every time, and very commercial looking.
NOTE: Store in a plastic bag in the refrigerator and use within three days or wrap them tightly in plastic, and they will keep frozen for several weeks. To serve tortillas that have been frozen: thaw and allow to come to room temperature, then wrap in aluminum foil and heat in a warm oven. Or wrap between damp paper towels and defrost in the microwave for approximately 1 minute.
NOTE: To reduce trans fats from this recipe, use trans fat free shortening.