Toast the cardamom pods in a heavy skillet for about 5 minutes over low heat, shaking the pan from time to time until the cardamom is very fragrant. Add the olive oil and butter and slowly heat to infuse the oil and butter with the cardamom flavor for about 10 to 15 minutes while the asparagus is cooking. Rinse the asparagus stalks and arrange in a heatproof plate, such as a pie or quiche pan, or in a steamer basket. (If using bamboo, line the basket with a piece of parchment or wax paper.) Fill a large pot or a wok with several inches of water and heat until boiling. If using a plate, set it on a tuna fish can with both the top and bottom removed. Or, set the steamer basket in the wok. Steam the asparagus 5 to 6 minutes, or until just tender. Remove and arrange on a serving plate. Pour the cardamom butter and sprinkle the salt over the asparagus and serve.