Stir together mashed potatoes, 1 teaspoon horseradish and flour; set aside.
Heat oil in a large skillet over medium-high heat. Make blini by dropping 1 tablespoonful of potato mixture into pan. Cook 2 to 4 minutes per side or until golden brown. Remove to a paper towel lined plate to drain. Keep warm in the oven. Repeat with remaining potato mixture.
In a small bowl, stir together sour cream, remaining horseradish, and dill.
Serve blini by topping each with 1 1/2 teaspoons sour cream mixture. Garnish with caviar.