Scrub clams thoroughly, discarding any cracked or opened shells.
Saute garlic in hot olive oil in a Dutch oven over medium-high heat until tender. Add tomatoes, and saute 1 minute. Add champagne; bring to a boil. Add clams; cover, reduce heat, and simmer 6 to 10 minutes or until clams open. With a slotted spoon, transfer clams, still in their shells, to a serving dish, discarding any unopened shells. Spoon cooking liquid over clams; sprinkle evenly with scallions, parsley, and pepper. Serve immediately.
*Note: 2 cups sparkling wine and 1 bunch green onions may be substituted.