Add the yeast and sugar into the water and mix well. Leave in a warm place for 10 minutes for the yeast to activate. Small bubbles will form and the mixture will become frothy.
Break eggs into a bowl or cup and add olive oil. Beat with a fork until the mixture is smooth and frothy.
Put the flours and salt in a bowl. Combine and make a well in the center. Add in the egg mixture, the vinegar and the yeast/water mixture. Stir until just combined. The batter will be thick and a little sticky.
Pour the batter into a lined and lightly greased loaf tin. Spread evenly with an oiled spoon. Place the tin into a large plastic bag and leave in a warm place to rise. It should take between one and two hours for the mixture to double in size.
Once the mixture has risen, remove from the plastic bag and bake at 375°F/190°C for 25-30 minutes.
Cool in the tin for 10 minutes then transfer to a wire rack to cool completely.
Store in an airtight container in the fridge for up to 5 days or in the freezer for a month.