Thaw and rise dinner rolls according to package directions. Melt butter in large non-stick skillet over medium heat until hot. Add leeks, salt and pepper; adjust heat to low. Cook 5 to 7 minutes or until the vegetables are soft and begin to brown. Set aside to cool.
In large bowl, combine beef, leeks, potatoes and cream cheese, mixing gently but thoroughly. Season with salt and pepper, as desired.
Preheat oven to 350°F. In small bowl, combine toppings.
Using rolling pin, roll out one dinner roll to 4-inch circle. Place 1/4 cup beef mixture in center of roll. Pull edges of dough over beef mixture, pinch the dough closed. With your thumb, create dent in middle of knish. Place knish on parchment-lined shallow-rimmed baking sheet. Repeat with remaining rolls. Brush each knish with egg; sprinkle topping mixture on each knish. Bake in 350°F oven 30 to 35 minutes or until knish is golden brown. Let knish rest 10 minutes before serving.
Nutrition information per serving: 200 Calories; 60.3 kcal Calories from fat; 6.7 g Total Fat; 2.6 g Saturated Fat; 0.1 g Trans Fat; 0.4 g Polyunsaturated Fat; 1.6 g Monounsaturated Fat; 42 mg Cholesterol; 405 mg Sodium; 25 g Total Carbohydrate; 0.3 g Dietary Fiber; 10 g Protein; 2 mg Iron; 184 mg Potassium; 0.1 mg Niacin; 0.2 mg Vitamin B6; 0.6 mcg Vitamin B12; 1.4 mg Zinc; 13.8 mcg Selenium; 36.5 mg Choline;