Spray 8 small custard cups or souffle dishes with nonstick spray. Place on baking sheet.
Heat chocolate and butter in large glass bowl resting over a pan of boiling water until butter is melted. Stir with wire whisk until chocolate is completely melted. Stir in sugar until well blended. Blend in eggs 1 at a time, so that the eggs do not cook. Stir in Hazelnut extract and flour.
Divide batter evenly among prepared and nonstick sprayed custard cups, about 2/3 to 3/4 of the way full.
Bake 12 to 14 minutes or until sides are firm but centers are soft. Let stand 1 minute.
Invert cakes onto dessert dishes and top with a little hazelnut liqueur and a spoonful of nutella on each lava cake.
Serve immediately, with a scoop of vanilla ice cream and chocolate shavings.