Reduce the heat, and just barely simmer for about 2 hours or until the stock is well flavored.
Place pan over low heat so that sauce just barely simmers.
I cover the tuna with oil in a pot, add two cloves of garlic, bring up the heat and then let it barely simmer for 10 minutes.
The water should barely simmer and never boil.
Stir in rice, cover, and reduce heat to very low so water barely simmers.
Place casserole over very low heat so juices barely simmer.
Watch the liquid so that it barely simmers.
Once the liquid returns to a boil, adjust the heat down so the liquid barely simmers.
Adjust heat so mixture barely simmers, and cook, stirring constantly, until it thickens, 2 to 5 minutes.
Reduce the heat so that the liquid barely simmers.