Method

Pastry: In bowl, whisk flour with salt. Using pastry blender or 2 knives, cut in butter and shortening until in coarse crumbs. In liquid measure, whisk egg yolk with vinegar; add enough ice water to make 1/3 cup (75 mL). Pour over flour mixture, stirring briskly with fork just until pastry holds together. Form into ball. Wrap with plastic wrap and refrigerate for 1 hour. (Make-ahead: Refrigerate for up to 4 days or enclose in resealable plastic bag and freeze for up to 2 weeks; thaw in refrigerator.)

On lightly floured surface, roll out pastry to (c)-inch (3 mm) thickness. Using 2-1/2-inch (6 cm) round cookie cutter, cut out 36 rounds, rerolling scraps as necessary. Fit into 1-1/2-inch (4 cm) tart cups. (Make-ahead: Cover with plastic wrap and refrigerate for up to 24 hours.)

Divide cheese and chives among shells. In bowl, whisk together eggs, milk, salt and pepper; spoon by scant tablespoonfuls (15 mL) into each shell.

Bake in bottom third of 400°F (200°C) oven until golden, about 20 minutes. Serve warm. (Make-ahead: Remove from pan; let cool on rack. Refrigerate in single layer in airtight container for up to 3 days; reheat on baking sheet in 400°F/200°C oven, about 4 minutes.)