Step 1Heat the oven to 375 degrees.
Step 2Cream 1 cup (2 sticks) of the butter with three-fourths cup brown sugar until light. Beat in the sweet potatoes, then the egg yolks and cream. Add the salt, cinnamon, ginger, nutmeg and cloves and mix well. Beat in the bourbon.
Step 3In a separate clean bowl, beat the egg whites until stiff. Add one-quarter of the whites to the sweet potato mixture and stir in well. Gently fold in the remaining whites. Pour into the pie crust.
Step 4Combine the remaining butter, the remaining one-fourth cup brown sugar, flour and pecans and beat until well mixed. Crumble the mixture evenly over the top of the filled pie.
Step 5Bake in the center of the oven until the top is golden brown and the filling is set, about 40 minutes. Cool completely before cutting.