Start by cooking your sweet potatoes until tender; you can bake them at 400°F for about 45 minutes, boil them for 20 minutes, or microwave them on high for 8-10 minutes. Once they are cool enough to handle, peel the skin off and mash them in a large bowl until smooth.

In the bowl with the mashed sweet potatoes, add in white sugar, ½ cup of melted butter, evaporated milk, beaten eggs, and vanilla bean paste. Stir these ingredients together until they are well combined and have a smooth consistency.

Pour the sweet potato mixture into your crockpot, spreading it evenly with a spatula. Make sure your slow cooker is set to low heat, preparing for a long, slow cook.

In a separate bowl, mix together 3 tablespoons of melted butter, chopped pecans, light brown sugar, and all-purpose flour to create your crunchy streusel topping. Blend until everything is combined, then sprinkle this topping generously over the sweet potato mixture in the crockpot.

Cover the crockpot and let it cook on low for 3 to 4 hours. You’ll know it’s ready when the topping is golden and the sweet potato mixture is bubbly and hot.

During the last 5 to 10 minutes of cooking, open the lid and add a handful of marshmallows on top of the casserole. Close the lid and let them melt slightly.