In a heavy, deep pot or an electric deep-fryer, heat the vegetable oil to 360 degrees F. Add the potatoes, in batches, and fry until golden brown, 8 to 10 minutes. Remove with a slotted spoon and drain on paper towels.
In a large, nonstick skillet over medium-high heat, heat the olive oil. Add the onion and season with 1/4 teaspoon of the slat and 1/4 teaspoon of the black pepper. Cook for 2 minutes. Season the shrimp with 1/4 teaspoon of the salt and the cayenne and add to the skillet. Cook, stirring, for 2 minutes. Add the ham, green peas, garlic, and the potatoes. Add the remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Cook for 3 minutes, then add the butter and cook, stirring, for 1 minute.
To serve, divide the mixture into 4 equal portions on serving plates and drizzle with the hollandaise.
In a stainless steel bowl set over a pot of simmering water (be careful not to let the bottom of the bowl touch the water), whisk the egg yolks with the lemon juice, hot sauce, and water until pale yellow in color. Season with salt and pepper. Remove the bowl from the pot and, whisking vigorously, add the melted butter 1 tablespoon at a time, whisking until all the butter is incorporated. Keep warm until needed.