For the black bean patties: Mash the beans in a large bowl, leaving some of the bean texture. Stir in the corn, oatmeal, taco seasoning and garlic. Stir to combine, taste and then season with a pinch of salt and a few grinds of black pepper. Fold in the egg. Cover the bowl and refrigerate for 15 minutes to hydrate the oats.
In a large nonstick pan, heat the oil on medium heat. When the oil begins to swirl a bit, use an ice cream scoop to portion the black bean mixture equally into 4 balls. Drop them into the pan, then press each into a patty shape with a spatula. Cook on one side until golden and a bit crisp, about 8 minutes. Flip and cook on the other side until slightly crisped, 5 to 8 minutes more. Remove to individual serving plates.
For the cream sauce: In a double boiler with the water boiling but not touching the pot above, add a piece of the butter, the yolks, lime juice, a splash of water and a pinch of salt. Whisk continuously while the butter melts, then add another piece of butter, working it in until it melts. Continue adding the butter pieces one at a time, whisking and melting between additions, until all the pieces are whisked in. Taste and adjust with salt if needed. Keep warm on the double boiler.
Divide the ham into 4 servings and place a portion on top of each black bean patty. Top each with an egg, drizzle over the sauce and sprinkle with pickles. Sprinkle the plate with cilantro and tomatoes. Serve warm.