Preheat oven to 350°F. Cut chocolate into small pieces and place in double boiler with oil. Melt chocolate, cool. Beat eggs and egg yolks with sugar until fluffy. Add cooled chocolate mixture to egg mixture. Add flour; beat unil fluffy and glossy, about 5 minutes.
Sweet Cherry Filling: Combine cherries, 1/2-cup water and 3 tablespoons sugar in heavy saucepan; bring to boil on medium-low heat. Combine cornstarch and cold water. Add to sweet cherry mixture, constantly stirring until boiling. Remove from heat; set aside until completely cooled.
Oil and flour 12 3-inch muffin cups. Fill each cup half full with cake mixture; add 1-tablespoon cherry filling to each, then add additional cake mixture to fill. Bake 15-20 minutes until center is wobbly and sides are cooked. Run a knife around edge of cakes to loosen; tip out onto plates. Garnish with confectioner’s sugar, if desired.
Make Ahead Note: Freezes well. Remove uncooked, filled muffin tin from freezer and bake at 350°F for 30-35 minutes