Creamy Caramelized Onions on Sweet Potato Scones

From Food and Drink 2000, I loved the flavour of these onions and they would work nicely with a bbq'd steak.  Here on the scones though their flavour is front and centre.

SCONES
1 large sweet potato, about 1 lb
1 tbsp olive oil
salt and freshly ground pepper
1 cup flour
1,2 tsp chopped fresh rosemary or a pinch dried
1 tbsp melted butter
vegetable oil for frying

CARAMELIZED ONIONS
1 tbsp olive oil
2 tbsp butter
6 cups thinly sliced Spanish Onions or Sweet Onions
1 tbsp granulated sugar
Salt and ground pepper
2 tbsp sherry vinegar
1/2 cup chicken stock
1/2 cup whipping cream
20 sage leaves, slivered

1. Preheat oven to 400F.  Brush potato with oil and seasonings.  roast for 40 to 50 minutes or until potato is soft.  Cool, peel and mash potato.
2. Measure out 1 cup potato into a bowl.   Combine with flour, rosemary, butter, salt and pepper to form a soft dough.
3. On a floured board, roll dough out to 1/4 inch thick.  Using a 2 inch round cutter, cut out scones. Re-roll leftover pastry.  Brush oil on skillet over medium low heat.  Cook scones in batches for about 2 minutes per side or until flecked with brown and cooked in the centre.  Drain on paper towels.   Serve hot or at room temperature.
4. For onions, heat oil and butter on medium heat until butter sizzles.  Add onions and saute for 3 minutes or until onions start to soften.
5. Sprinkle in sugar, salt and pepper, reduce heat to medium low and continue to cook, stirring occasionally until onions turn golden brown, about 20 minutes. 
6. Stir in vinegar, stock and whipping cream.  Raise heat and reduce until onions become a thick mass, about 4 minutes.  Stir in sage.  Season to taste.  Cool.
7. Top the scones with the caramelized onions