Preheat the oven to 350 degrees. For the croutons, grease a jellyroll pan and place the slices of 6 okra pods in a single layer. Drizzle with the olive oil and roast for 22 minutes. Set aside to cool.
For the stew, in a Dutch oven over high heat, melt the butter and vegetable oil, then add the leeks, jalapeno peppers, salt, and cumin. Sauté until the leeks soften, around 3 minutes.
Add the stock, the beans and their liquid, tomatoes, the remaining okra, corn, squash, and tomatillos. Bring to a boil, then reduce the heat and simmer for 20 minutes. Season with the pepper and additional salt if needed.
Serve warm garnished with the cilantro, sour cream, and the roasted okra croutons.