Method

Place a small oven proof frying pan (around 20cm) on a medium heat, add a tablespoon of olive oil then add the potatoes and onion. Turn the heat down to low, sprinkle over a little salt and cook for around 25 minutes or until the potatoes are cooked through and lightly golden. Don’t stir too much just turn everything occasionally until ready.
Meanwhile, make the aioli. Crush the half garlic clove and a good pinch of salt to a paste in a pestle and mortar. Scrape into a medium sized mixing bowl and add the egg yolk. Mix the oils together in a measuring jug. Whisking all the time slowly and carefully pour the oils into the egg yolk mixture, continue beating and once thickened add half of the lemon juice. Continue beating until all the oil is added. Taste the aioli and add more lemon juice if needed then season with salt and pepper. Cover and place in the fridge until needed.
Pre-heat the oven to 200c/400g/gas mark 6. Crack the eggs into a large bowl, season and whisk well. Tip the cooked potatoes and onions into the bowl and mix everything together well. Return the mixture to the pan and place back on the hob to cook for around 20 minutes on a low heat or until the egg is setting. At this point you can place the pan in the oven and cook for a further 5-10 minutes until completely cooked all the way through or you can flip out the nearly set tortilla on to a board or plate and then pop it back into the pan to continue cooking. When it’s ready turn out the tortilla onto a board to cool.
You can serve the tortilla in the sandwich whilst it’s still warm or you can have it completely cooled. Warm the baguettes if you prefer and cut them in half. Spread a little aioli on to the bread and season with pepper. Cut the tortilla into pieces and place a few pieces into each baguette. Add a few slices of tomatoes and onions to each and serve.