Unroll the pie crust and fit it to a 9-inch pie plate. Scallop or crimp the edges.

In a small bowl, combine the 1/2 c. brown sugar, 1/3 c. finely chopped walnuts, and butter.

Carefully spread it onto the bottom of the pie crust.

In a large bowl, combine the pumpkin puree, sweetened condensed milk, cinnamon, pumpkin pie spice, ginger, clove, and eggs.

Pour into the pie crust.

In a small bowl, combine the flour, brown sugar, oats, walnuts, and cinnamon.

Grate the butter into the bowl, and mix with a fork until mixture is crumbly.

Sprinkle with water, mixing until lightly moistened.

Sprinkle the streusel evenly over the pumpkin filling, starting with the edges, and working toward the center.

Bake at 350 degrees for 45-50 minutes, or until a knife inserted near the center comes out clean.

Remove to a wire rack to cool completely. Cut and serve!