Saute the onion in a pan until golden brown. I used a dry fry pan but you can use a little drop of oil of you prefer. Once beginning to turn golden, turn off the heat and allow to cool while you carry on with the next step.
Drain the beans well and add them to a large bowl. Mash roughly with a potato masher. You just want them a bit crushed not completely pulverized.
Drain the artichoke hearts and chop into small chunky pieces, then add them to the crushed beans.
If using old-fashioned or rolled oats, pulse them a few times in a food processor or blender to make them smaller but still a bit chunky. If using quick oats you can skip this step.
Add the oats to the beans then add the onion, garlic, rosemary, lemon zest, salt and pepper.
Use clean hands to squeeze and squidge everything together really well.
Shape into 4 patties and really squeeze and compact them together well. Then place on a parchment paper lines baking tray or plate and refrigerate for at least one hour. It's fine to leave them up to a couple of days but if you do make sure to cover them with plastic wrap so they don't dry out.
To cook on a grill
Place on a grill over medium heat and leave to cook until a nice crust develops then turn over. They should take 5 to 6 minutes each side. Remove from the grill and serve immediately.
To cook in an oven
Put the burgers on a lined baking tray and cook at 350°F for 25 to 30 minutes, making sure to turn them over half way. They should be crusty and golden once ready.
To cook in a skillet
Heat the skillet with a small drop of oil. When hot add the burger patties.
Cook for 5 to 6 minutes until a nice golden crust has formed then turn over and do the same on the other side.
Be sure to drain the beans and the artichokes well. It doesn't hurt to give the artichokes a little squeeze to get the excess moisture out.
The oats are necessary for absorbing moisture and also for texture. I don't recommend switching them for anything else.
Don't be tempted to add the juice of the lemon as well as the zest. Moisture needs to be kept to a minimum here.
These burgers need the refrigeration step so don't skip it.
To store - Burgers keep well in the fridge for four to five days whether cooked or uncooked. Be sure to keep them wrapped well or in an airtight container so they don't dry out.To freeze uncooked burgers - Shape the burgers then lay them out on a lined baking tray and pop the whole thing in the freezer. As soon as they are hard you can transfer them to a freezer bag or container. Don't forget about them and leave them on the tray uncovered for too long though as they may get freezer burn.To freeze cooked burgers -Allow to cool completely then lay out on a lined baking tray and pop the whole thing in the freezer until they are hard. Then remove and put into freezer bags or containers. Or Stack the burgers with sheets of parchment paper between them and freeze. Either way will ensure they don't stick together.To reheat previously cooked burgers - Bake them in the oven at 370°F for about 15-20 minutes or until piping hot. If frozen bake them straight from the freezer for about 20-25 minutes or until piping hot all the way through.