Preheat your oven to 375 degrees F. This ensures that the sweet potatoes cook evenly and develop that lovely caramelization.
In a small bowl, combine 1/4 cup unsalted butter, 1 tablespoon brown sugar, 1 teaspoon cinnamon, and 1/4 teaspoon salt. Mix well until thoroughly combined. This buttery mixture will add moisture and flavor to your sweet potatoes.
Next, take the butter mixture and place it on a sheet of plastic wrap. Form it into a small rectangle or square. This will make it easier to slice into small pats later on. Once formed, place it in the freezer for 20 to 30 minutes until firm.
While the butter is chilling, take your 4 large sweet potatoes and carefully slice them. Make cuts every 1/8 to 1/4 inch deep, stopping about 3/4 of the way down the potato. This is crucial for achieving that hasselback style. A helpful tip is to slice halfway down the potato first, and then go back to slice deeper.
Once you've sliced the sweet potatoes, remove the butter from the freezer. Using a sharp knife, slice the butter into very thin pieces, then cut those in half. Aim for about 24 to 30 small, thin pats of butter.
Gently pull apart the sweet potatoes and place a butter pat into every three or four slices. This ensures that every bite has that delicious buttery flavor.
If desired, sprinkle the sweet potatoes with additional cinnamon for an extra kick of flavor. Then, place the potatoes in a baking dish so they stand upright. This allows for even cooking.
Now, let’s make the crumble! In a separate bowl, combine 2/3 cup brown sugar, 2/3 cup old fashioned rolled oats, 1/2 teaspoon cinnamon, and 1/4 teaspoon salt. Mix well to combine, then add in 2 tablespoons flour.
Using your hands, crumble in another 1/4 cup unsalted butter and mix until the entire mixture is moistened and comes together. This crumble will sit beautifully on top of your sweet potatoes.
Spread an equal amount of crumble over each potato, pressing gently but firmly to ensure it sticks. This will create a delicious crust as they bake.
Bake the sweet potatoes for 30 to 35 minutes. After that time, cover them with foil and bake for another 20 to 25 minutes. This will ensure they are tender and flavorful.
To serve, carefully cut each sweet potato in half and enjoy the beautiful layers of flavor and texture.
