Preheat the oven to 350°F (175°C). Lightly grease a 9-inch square baking dish.
Whisk together the pumpkin puree, eggs, evaporated milk, brown sugar, vanilla, cinnamon, ginger, nutmeg, cloves, and salt until smooth and creamy.
Pour the pumpkin mixture into the prepared baking dish and spread it into an even layer.
For the streusel, combine the oats, flour, brown sugar, cinnamon, salt, and chopped pecans in a separate bowl. Pour in the melted butter and stir until the mixture forms moist, crumbly clusters.
Sprinkle the cinnamon streusel evenly over the pumpkin filling, covering the surface without pressing it down.
Bake for 40 to 45 minutes, until the pumpkin filling is mostly set and the streusel is golden brown. The center should have a slight jiggle when gently moved.
Let the crisp cool for at least 15 minutes before serving so the filling can finish setting.
Serve warm with whipped cream or vanilla ice cream.