1. Preheat oven to 325 degrees. Lightly toast bread on a baking sheet until just beginning to crisp, 5 to 6 minutes. Let cool.

2. Meanwhile, stir together cream cheese and creme fraiche until smooth. Make about 80 small cucumber balls using a mini melon baller (1/2 inch) or a Parisian scoop.

3. Arrange toasts on a work surface. Spread a thin layer of cream cheese mixture onto toasts. Cut each toast into 3 rounds using a 2-inch cookie cutter. Divide 1 ounce salmon roe among half the toasts. Top remaining toasts with cucumber balls and remaining ounce salmon roe. Serve immediately.