Trim stems of artichokes, leaving a flat bottom, so the artichokes will sit upright; cut off top 1/3 of each.
With scissors, trim tips of remaining outside leaves.
With spoon or melon bailer, remove fuzzy choke and enough of center to make generous hollow.
In a large saucepan, set artichokes upright in small amount of boiling salted water.
Simmer 30 to 40 minutes or until tender.
Drain upside down on paper towels.
Add water to reserved mushroom liquid to make 2-1/2 cups liquid.
Cook contents of rice and seasoning packets with mushroom liquid according to package directions.
Add mushrooms to hot cooked rice.
Pile rice into artichokes.
Combine melted butter or margarine with lemon juice.
Spoon about 1 tablespoon of lemon-butter over each artichoke.
Divide remaining lemon-butter among 6 individual cups for dipping artichoke leaves.