Flatten muffin liners; place on a baking sheet. Place a wafer on each. Scoop 1/4 cup of ice cream onto each wafer; freeze.
Meanwhile, in a small heavy saucepan, combine the egg whites, sugar and cream of tartar; beat on low speed with a portable mixer for 1 minute. Continue beating over low heat until mixture reaches 160°, about 12 minutes. Remove from the heat; add vanilla. Beat until stiff peaks form and sugar is dissolved, about 4 minutes.
Remove baking sheet from freezer; immediately spread meringue over ice cream, sealing to edges of wafers. Broil 4-6 in. from the heat for 1-2 minutes or until meringues are lightly browned. Serve immediately.