Wash the sweet potatoes and put them on a foil or parchment lined baking sheet. Bake in a preheated 350* F. oven for 1 - 1 1/2 hours until they are very tender. Remove from the oven and allow to cool briefly before peeling. Put the peeled sweet potatoes into the large bowl of an electric mixer fitted with beaters or a whip attachment. Mix the hot sweet potatoes on low speed to begin mashing them. Add the butter and mix until it is absorbed . Add the salt, nutmeg, honey, and both sugars and mix until they are thoroughly blended. Add the lightly beaten eggs and vanilla and beat on medium speed for 2 minutes. Reduce mixer speed to low and slowly add in the heated milk. When the milk is incorporated, taste carefully for seasoning and add more salt, nutmeg, or sugar as needed. Thoroughly butter a 9x13x2 baking dish with the softened butter and pour the sweet potato mixture into it.
Put the brown sugar, flour, baking powder, cinnamon, nutmeg, and salt into a mixing bowl and mix well. Use your fingers to work the chilled butter into the mixture until it resembles oatmeal with some large pea size pieces of butter in it. Stir in the pecan pieces and mix well. Sprinkle the mixture evenly over the top of the sweet potatoes and bake in a preheated 375* F. oven for 30 to 45 minutes until the topping is golden brown and crisp and the sweet potatoes are set but still slightly loose in the center. Serve hot.