Cook your sweet potato until easily pierced with a knife. Set aside to cool.
Once the sweet potato is cool enough to handle, peel off the skin and place the flesh in a blender.
Add the butter, flour, salt, and curry to a large pot over medium heat, stirring occasionally, until you have a roux.
Add 4 cups of milk, a little at a time, whisking and stirring after each addition to remove any lumps.
Once all the milk has been added, carefully add the pureed sweet potato. Stir until fully incorporated.
If desired, add the pepper and frozen peas. Remove the soup from the burner and allow to sit for about 5 minutes until the peas are cooked.
This recipe reheats really well! Store in an airtight container in the fridge for up to a week or in the freezer for at least 6 months. Thaw in the fridge the night before you eat it. Reheat on the stove and add a splash of milk, if needed!