Free-Form Open-Faced Potato Tart

Preheat oven to 400ºF (200ºC).

In bowl, stir together flour, salt and cayenne. Using pastry blender or 2 knives, cut in butter and shortening until mixture is in fine crumbs with a few larger pieces.

Stirring with fork, pour in vinegar and enough of the water to make dough hold together. Press into disc; wrap in plastic wrap and refrigerate for 30 minutes.

Prepare the filling. (see filling recipe)

On lightly floured surface, roll out pastry into 16-inch (40 cm) circle; place on pizza pan. Spread potato mixture over pastry, leaving 2-inch (5 cm) border uncovered. Arrange tomatoes over filling; sprinkle with Parmesan. Fold border over top, pleating to fit. Brush pastry with remaining egg.

Bake in bottom third of oven for 40 to 45 minutes or until pastry is golden. Let stand on rack for 10 minutes before cutting.

Meanwhile, cut each tomato lengthwise into 1/2-inch (1 cm) thick slices; place on foil-lined baking sheet. Sprinkle with pinch each of the salt and pepper; broil for 5 minutes per side or until slightly shrivelled and edges are blackened. Set aside.

In large saucepan of boiling salted water, cover and cook potatoes for 20 minutes or just until tender. Drain and let cool. Slice thinly crosswise and set aside.

Meanwhile, in skillet, heat oil over medium-high heat; cook onions, garlic, rosemary and remaining salt and pepper, stirring occasionally, for 5 minutes. Reduce heat to medium.

Cook for 5 minutes longer until onions are golden. Transfer to large bowl. Add potatoes, Asiago cheese and all but 1 tablespoon (15 mL) of the eggs; toss gently to combine.