Preheat the oven to 425 degrees Fahrenheit. Wash and dry sweet potatoes. Use a fork and poke the sweet potatoes all over. Place the sweet potatoes on a lined sheet pan and bake in the preheated oven for 45-50 minutes, until the sweet potatoes have softened. Remove from the oven and allow the sweet potatoes to cool.
Reduce the heat of the oven to 350 degrees Fahrenheit.
Once the sweet potatoes are cool enough to handle, remove the skin from the sweet potatoes and place the sweet potatoes in the bowl of a stand mixture. Beat the potatoes on low speed until smooth. Add granulated sugar, eggs, butter, heavy cream, vanilla extract, and kosher salt, and beat the mixture for about 1-2 minutes until combined. Pour the mixture into a 2-quart baking dish and set aside. Rinse and dry the bowl of the stand mixture.
Next, prepare the topping by combining cold butter, brown sugar, all-purpose flour, oatmeal, and ground cinnamon in the bowl of the stand mixture. Beat the mixture on low speed until combined, and it starts to stick together, about 1 minute. Break the topping up and place the topping over the sweet potato mixture in the baking dish.
Bake in the preheated oven for 55 minutes to 1 hour, until the top is golden and the bottom is bubbly around the edges. Remove and allow to cool for 5 minutes before serving.