1. Before making the hollandaise, make the vinegar reduction by putting all the ingredients in a pan over a medium heat. Reduce until 50ml of liquid remains, strain and set aside.
2. Add the yolks, whole eggs and vinegar reduction to a double boiler (or a bowl set over a pan of simmering water) to make the hollandaise. Whisk until the mixture has doubled in volume then take off the heat.
3. Gradually add the cream to the egg mixture until it is thoroughly combined.
4. For the pastry, rub together the flour and butter (or mix in a food processor) until you have a sandy consistency.
5. Combine the egg, milk and salt in a jug, then add to the flour and butter. Mix to form a dough, wrap in cling film and chill in the fridge for 30 minutes, or until ready to use.
6. Set the oven to 185°C/165°C fan/Gas Mark 4.
7. Roll out the pastry to a 3-5mm thickness on a lightly floured surface so that it will fit a 12 inch round fluted tin with a removable base. Make sure the pastry overhangs the edges of the tin slightly, as it will shrink in the oven.
8. Use a fork to prick the base of the tart. Line with parchment paper (or cling film) and baking beans before placing in the oven for 20 minutes to bake blind.
9. Carefully lift off the lining paper and beans before returning to the oven for a further 10 minutes. The pastry should be cooked to a light golden brown.
10. Use the beaten egg to brush over the pastry case, and use a sharp knife to carefully trim and neaten up the edges.
11. Reduce the oven temperature to 170°C/150°C fan/Gas Mark 3.
12. Peel and blanch the asparagus spears in salted boiling water for 2 minutes. Remove and place in a bowl of iced water to refresh and stop the cooking process.
13. Fill the pastry case with the hollandaise sauce and place the asparagus on top.
14. Bake for 20-25 minutes until lightly set, before leaving to cool in the tin. Remove from the tin and garnish with the chives and, if using, the edible flowers.
For more inspiration and tips visit the Organic UK Facebook page.