Heat oven to 325°F and line 18 muffin cups with liners.
Mix the crumbs and butter and press 1 heaping tablespoon into each liner.
Beat the cream cheese and sugar until smooth. Beat in the sour cream, vanilla and flour, then the eggs one at a time just until combined.
Spoon about two-thirds of the batter into the cups and sprinkle with chocolate chips.
Stir the Nutella into the remaining batter and spoon on top. Swirl with a toothpick.
Bake 20 to 24 minutes, until just set. Cool, then chill at least 3 hours.