Spanish burger with pickled shallots

Ingredients:

Burgers

• 0.6 kg of beef shoulder blade,
  cut into 5 cm pieces (or take 0.7 kg of ground beef with 20% fat and exclude lard)
• 110 g pork fat (omit if using ground beef)
• 1 tbsp. l. rapeseed oil
• 4 slices fontina cheese
• 4 soft sesame seed buns, lightly toasted
• Arugula, for serving

Hot oil

• 110 g unsalted butter
• 1 tbsp. l. harissa (chili paste)
• 2 cloves garlic, crushed

Pickled Shallots with Saffron

• 3/4 cup sherry vinegar
• 1 tbsp. sugar
• A pinch of saffron
• 2 large shallots, thinly sliced

Aioli

• 1/4 cup mayonnaise
• 1 tsp. harissa (chili paste)
• 1/4 tsp smoked paprika
• 2 canned piquillo peppers (or 1 roasted red pepper), drained
• 1 anchovy fillet
• Juice of half a lemon

Crispy prosciutto ham

• 4 thin slices prosciutto ham
• 0.5 cups of rapeseed oil

Preparation:

1. Prepare hot oilMelt the butter in a small saucepan over low heat. Add the harissa and garlic and sauté for 1 minute. Remove from heat, cover, and let sit for 1 hour to allow the flavors to meld.
2. Make pickled shallots with saffronIn a small saucepan, combine the vinegar, sugar, 1 teaspoon of salt, and saffron and bring to a boil over medium heat. Remove from heat and let cool for 10 minutes. Place the shallots in a small bowl, pour the marinade over them, cover, and refrigerate for at least 30 minutes and up to 24 hours.
3. Prepare the aioliIn a blender, combine the mayonnaise, harissa, smoked paprika, piquillo pepper, anchovies, and lemon juice until smooth; season with salt and pepper to taste. Cover and refrigerate for at least 30 minutes to allow the flavors to meld.
4. Make Crispy ProsciuttoHeat canola oil in a small skillet over medium heat until shimmering. Add prosciutto slices one at a time and cook until crispy. Transfer to a plate lined with paper towels to drain.
5. Prepare the cutletsGrind the meat and lard through a large meat grinder into a large bowl (or place the ground beef in a large bowl). Season with salt and black pepper. Form the ground beef into 4 equal patties.
6. Heat a cast-iron skillet over high heat until smoking. Add canola oil, add the patties, and cook until golden brown on the bottom, about 4 minutes. Flip and begin brushing with hot butter.
7. Cook until the patties are browned on the other side and cooked through to medium-rare, about 4 more minutes. Place a slice of cheese on top of each patty, add a splash of water to the pan, quickly cover with a lid, and cook until the cheese is completely melted, about 1 minute.
8. Spread a little aioli on the top and bottom halves of the bun. Place a patty on each bottom half; top with some pickled shallots, then a slice of prosciutto and some arugula. Top with the top half of the bun and serve.