Heat milk in a small pan over medium heat. Whisk vigorously until foam is stiff. Alternatively, use a milk frother to whisk until stiff. Divide coffee between 2 cups. Using a spoon to hold back foam, pour hot milk into each cup. Using the tip of the spoon, place 8 small dots of milk foam in a heart shape on top of each coffee. Drag a toothpick through foam dots, following the shape of the heart and also creating hearts out of each foam dot. Serve immediately.