Step 1

Grease a 19 cm round cake pan, line base with baking paper and set aside.

Step 2

Place onions in large, heated, oiled saucepan and cook, stirring, until soft. Stir in sugar and vinegar, cook over low heat for 10 minutes or until golden brown, stirring occasionally.

Step 3

Fry bacon in pan until crispy. Add spinach leaves to bacon pan at end of cooking, to wilt leaves.

Step 4

Boil, steam or microwave potatoes until tender, then drain.

Step 5

Slice potatoes thickly, place in layers in prepared pan. Top with caramelised onions, spinach and bacon on each layer.

Step 6

Combine milk, eggs, cheese and thyme then pour over onions.

Step 7

Bake, uncovered, at 180C for 35 minutes or until frittata is firm.

Step 8

Cut into wedges and serve hot or cold with salad.