Place the flower heads and cream into a small microwave safe glass bowl. Cook in the microwave on High until hot to the touch, 20 to 30 seconds. Once hot, stir the flowers with a spoon, and set aside to steep 5 minutes. Return to the microwave, and cook 10 to 20 seconds to reheat. Stir again, and set aside to steep 5 minutes more. Repeat the heating-stirring-steeping process two more times until the cream is strongly flavored with lavender.
Combine the bittersweet chocolate with the semisweet chocolate in a microwave safe glass bowl. Divide the chocolate into equal portions, and set one portion aside. Cook the remaining chocolate in the microwave on High in 20 to 30 second increments until melted, stirring between each heating. Using a fine-mesh strainer, strain the cream into the melted chocolate; discard the flower heads and bits of lavender. Stir the cream and chocolate together until smooth. Chill in the refrigerator until somewhat firm, but not hard, about 1 hour.
After the lavender chocolate mixture has chilled, place the remaining chocolate and butter into a microwave safe glass bowl. Cook in the microwave on High in 20 to 30 second increments until just melted, stirring between each heating; set aside.
Line a baking sheet with a piece of waxed paper.
Roll the lavender mixture into 1 tablespoon-sized balls, and dip into the melted chocolate mixture using a skewer or toothpick.
Place onto the prepared baking sheet, and chill in the refrigerator at least 2 hours to harden.
