Combine your paprika, black pepper, salt, onion powder, garlic powder, ground allspice, oregano and cayenne in a bowl.
Take 2 tbsp of the spice mix and combine with your buttermilk in a large bowl.
Butterfly your chicken breasts and place in the bowl. Stir to coat the chicken, then leave in the brine overnight preferably, or for at least 4 hours.
Place your yeast, water and milk in the bowl of a stand mixer and leave to bloom for 5 mins.
Add your sugar, salt, egg, butter and flour to the stand mixer and mix on a medium speed. Once all incorporated as a dough, turn up the speed to work the dough for 5 mins. By this time it should be smooth and tacky to touch.
Place your dough in a slightly oiled bowl and cover with cling film. Leave to rise in a warm place for about an hour, or until doubled in size.
Remove half of your dough from the bowl. On a lightly floured square of parchment, roll out to half inch thickness in a round on your workbench, then cut out with a medium sized bowl. Cut out another circle with a 3 inch cutter.
Leave your donut to rest for 10 mins whilst you heat 3 inches of vegetable oil in a large wide saute pan and heat it to 175°C/340°F.
Gently shimmy your donut off your greaseproof paper into the oil. Fry for about 3 mins on one side until deeply golden, then flip and cook for a further 3 mins on the other side. Remove from the oil and drain on a rack and leave to cool. Repeat with your remaining dough.
Combine your butter, icing sugar, vanilla essence and evaporated milk in a bowl until you have a smooth sauce.
Pour your glaze over your donuts until they are fully coated. Leave to dry.
Combine the rest of your seasoning with your flour in a bowl, and beat your eggs in a separate bowl.
Remove your chicken from the buttermilk and dredge in the flour, then egg, then flour in turn. Leave to rehydrate on a tray.
Heat your vegetable oil to 180°C in a wide saute pan. Fry your chicken for about 10 mins, turning repeatedly until it is evenly golden and crisp.
Top your donut with your chicken breasts, then the other donut. Serve immediately!