These are irresistible!!

Makes about 45

For the Dough:

3+1/2 cups all-purpose flour, plus extra if needed
Pinch of salt
2 & 1/2 tsp baking powder
1 cup corn or olive oil
4&1/2 oz unsalted butter, softened at room temperature (it should be really soft to touch)
2 tbsp apple cider or red wine vinegar
1 cup plain yoghurt
1 cup finely (but not too finely) chopped walnuts (you should feel the bite)
1 cup pitted sliced black olives (Kalamata)
To Glaze
1 egg yolk, beaten
Preheat the oven to 375 F . Lightly grease the bottom of a large baking sheet.
In a large mixing bowl, combine the oil, butter, vinegar and plain yoghurt. Stir to mix. Add the walnuts and olives and stir to combine.
In a medium bowl combine the flours, salt and baking powder. Stir to mix.Add the flour mixture to the walnut/olive mixture. if the dough is sticky, gradually add more flour and knead the dough until it is tender and pleasant to the touch but not too tight or sticky.
Taking a little at a time, shape into balls about the size of a big whole walnut.
Arrange the balls on the prepared baking sheet. Brush their tops with the beaten egg yolk.
Bake until golden, about 40 minutes.
Bring to room temperature before serving. 
The inside of these mini breads should appear moist, it’s normal!