Honestly, these beetroot and black bean burgers will have children and adults alike devouring them with gusto. Quite apart from looking the part, the combination of beetroot and black bean offer up a delicious and inexpensive alternative to beef burgers. Beetroots are root vegetables and naturally sweet tasting, they also happen to be exceptionally good for you. Beetroots also do a grand job of staining your hands and tongue. What’s not to love? Serve in a bun, with gherkins and sour cream, mustard for the grown ups, perhaps some ketchup for the kids.
Cook the onion in a small saucepan with the olive oil until soft and translucent, about 8–10 minutes, then add the garlic and cook for 2 minutes more, until fragrant. Remove from the heat and set to one side.
Combine the grated beetroot, beans, mustard, spices, dill, oats/breadcrumbs and seasoning in a bowl. Use your hands to work the mix together until cohesive and easily shaped.
Shape the mix into burgers about 2cm thick and place them on a tray or plate. Put them into the fridge to firm up for an hour or so.
Heat a large non-stick frying pan with enough oil to cover the surface of the pan and about 1cm deep, and fry the burgers over a moderate heat for 2–3 minutes on each side, until crisp and the interior is hot. Remove from the heat and serve immediately.
To make the aïoli, place the egg yolk, garlic and mustard in a small bowl and beat together.
Slowly add the olive oil in a steady stream, whisking vigorously all the time until it thickens, adding salt, pepper and lemon juice to taste.