Preheat oven to 375 degrees.

Place the sweet potatoes in salted water to cover. Bring to a boil.

Place the butter in a medium bowl and place it over the saucepan to melt the butter. Remove when melted and let the potatoes continue to cook. When fork-tender, drain well.

Using a potato ricer, rice the sweet potatoes into the melted butter. (Alternately, use a food mill.) Add the coconut sugar, half-and-half, vanilla extract, egg and a pinch of salt and mix well to combine.

Unroll the pie crust onto a piece of parchment paper. Spread the sweet potato mixture over the pastry, leaving a 2 to 3-inch margin.

Roll the edges of the pie crust over the filling, tucking it in every inch or two.

Combine the pecans, flour, brown sugar and butter in a small bowl. Sprinkle it over the galette.

Bake for 10 minutes. Reduce the heat to 350 and continue baking another 20 minutes or until the crust is golden. If the nuts look like they may brown too much or possibly burn, cover the center with a small piece of aluminum foil.

Cut into wedges and serve.