This soup also makes a wonderful vegetarian main dish by swapping out the chicken stock for your favorite vegetable broth. And of course, omit the optional crispy prosciutto.
Preheat the oven to 400°F.
In a large Dutch oven, heat the olive oil, onions, and a generous pinch of salt & pepper over medium heat, letting the onions warm and cook slowly to coax out their flavor. When they are translucent and starting to get a tinge of golden color, add the garlic and oregano and stir until their fragrances release. Add the split peas, stock, bay leaves, and 5 cups of water. Bring to a boil, then reduce heat and let simmer, partially covered, for 40 minutes.
Meanwhile, slice the lemon into very thin rounds and remove the seeds. Toss with the remaining olive oil and a bit of salt. Line them up on a rimmed baking sheet lined with parchment and scatter the feta. If you’re using the prosciutto, pile them on the sheet in little clusters and drizzle a bit more olive oil over the top. Sprinkle some salt and roast for 15-20 minutes. Remove from the oven to cool a bit. Leave the lemon slices on the baking sheet to continue cooling, but break up the prosciutto into pieces and put in a bowl with the baked feta, almond slivers, and mint. Stir the mixture to make a gremolata.
When the peas are cooked, Stir in the sherry vinegar and adjust for seasonings. Serve in deep bowls with a dollop of yogurt and a slice or two of baked lemon topped with a spoonful of the gremolata mixture. For a last flourish, garnish with a bit of Aleppo pepper. Savor with delight and gratitude.