Chimichurri: add the herbs, diced shallot and chopped garlic to a food processor or blender and pulse until chopped and incorporated. 

Pour in 3/4 cup olive oil and 1/4 cup of red wine vinegar into the food processor and pulse until you have a blended sauce with a soupy consistency. 

Taste your chimichurri at this point and add salt and pepper until it tastes the way you'd like. 

If you think it's too chunky, you can add up to another quarter cup of olive oil or vinegar and pulse again to change the thickness of the sauce. 

Store in the fridge for about 2 to 3 weeks. If you're pulling it straight out of the fridge to use, it might be extra thick. Allowing the chimichurri to come closer to room temperature will bring it back to an oilier texture. 

Caramelized onions: add 1 tablespoon of butter to a large pan over medium heat. 

When butter is bubbly and frothing, add your sliced onion. 

Add a pinch of salt and stir everything to combine. 

Reduce heat to medium-low and cook onions, stirring often for 20 minutes. 

After 20 minutes, your onions should be tan-colored, but not browned. You might start to see dark brown spots forming on the bottom of the pan though, and if you do see that, add a tablespoon of water or two to the pan with the onions and use that water to stir the dark parts at the bottom to keep things from burning. 

Continue cooking the onions over medium-low heat for another 10 or 15 minutes. Remember: if you see dark spots or dry areas on the pan, add a tablespoon of water. The water should cook off quickly, but it will help to temper the pan temperature and help the onions to cook through without burning. 

After the onions are nice and brown, remove from the pan to a sealed container and if not serving immediately, store in the fridge for no more than a week or so. 

Loose meat/ground steak: in a large skillet over medium-high heat, brown the ground beef, attempting to break it up into smaller crumbles while it cooks.

While the beef is browning, add your flour and water to a medium bowl and whisk to combine. 

When the beef is mostly cooked and there is no visible pink on the meat, whisk the flour and water mixture one more time and add it to the skillet with the beef. Reduce the heat under the pan to medium-low and cook until the liquid has boiled off. Continue mashing and breaking the meat into smaller pieces while it is cooking. This should take another 8 to 10 minutes or so.

After the liquid is mostly gone, remove the pan from the heat.

Sandwich assembly: toast your buns if desired.

Scoop 1/4 of the caramelized onion and add to each bottom bun half. Top the onions with 1/4 of the loose meat mixture and then spoon over a bit of chimichurri. Add the top bun and serve.