Preheat oven to 350°F. Brush an 8-inch spring form pan with 1 tablespoon melted butter. Mix remaining butter with graham cracker crumbs, sugar and salt in a bowl. Press mixture into the bottom and up the sides of the pan. Bake until golden brown, about 15 minutes. Cool on rack.
Halve and pit avocados; scoop out flesh and chop. Transfer to a bowl, add cream cheese and beat with a mixer on medium speed until smooth. Add condensed milk, lime and lemon juices, and salt; beat until fluffy, scraping bowl as needed. Pour filling into the crust, press a piece of plastic wrap directly on the surface. Chill for at least 4 hours. Remove spring form ring. Slice and garnish with whipped cream. Serve immediately. Serves 8.
Approximate Nutrient Analysis per serving (not including whipped topping):
420 calories, 23 g fat, 11 g saturated fat, 50 mg cholesterol, 350 mg sodium, 47 g carbohydrate, 3 g fiber, 36 g sugar, 8 g protein