Begin by sautéing the rice in a pan with 3 tablespoons of olive oil, the chopped onion, garlic, tomato sauce and salt and pepper to taste. Stir often.
When the onion and rice have become slightly translucent, pour in the water or chicken stock to the rice and bring to a simmer. Cook on medium-high until the water evaporates and the rice is half-cooked, then take off the heat to cool slightly.
Meanwhile, roast the banana leaves you'll be using to wrap the pasteles by running them over the stove flame so they soften and become more pliable. This step will also give a deeper flavor to the pasteles after cooking!
Cut the banana leaves into 12 x 16 inches (30 x 40 cm) rectangles and prepare the kitchen twine to have handy while we assemble the pasteles de arroz. (If you don't have access to banana leaaves parchment paper works well too.)
Take a big cucharón of rice (or a heaping serving spoon full) and place it in the center of a cut banana leaf, forming a little rectangle.
Place a spoonful of stewed meat on top of the rice and fold the leaf around the filling twice lengthwise. Then, fold the top and bottom sides towards the middle and tie them securely with string.
Careful not to wrap the pasteles up too tightly! Leave a little bit of space for the rice to expand, otherwise the leaf might split while boiling.
To cook our pasteles, bring a large pot of salted water to boil and add them to the pot. Leave them to cook for 45 minutes to 1 hour.
Once the rice has become tender, drain the pasteles, remove the leaves and serve!