For Sweet Dough: Combine water and yeast in a bowl, hand-whisk to mix, set aside and let stand a few minutes. In the mixing bowl of electric mixer, cream butter and sugar together until fluffy. Mix in egg and vanilla. Stir in the water-yeast mixture, milk, salt, and 2 cups of the flour. Switch to dough hook and knead on slow speed, sprinkling in as much of the remaining 1/2 cup flour as needed, until dough is smooth, about 5 to 8 minutes. Cover bowl with a towel and let dough rise in warm, draft-free place 45 to 60 minutes, or until almost doubled.

For Gooey Butter Topping: Combine granulated sugar, butter, salt, egg, corn syrup, flour, water and vanilla in work bowl of food processor fitted with metal blade; process 20 to 30 seconds, or until mixture is a smooth paste. (Or beat with electric mixer until well mixed.)

To Assemble: Generously spray two 9-inch square baking pans with nonstick cooking spray. Line a baking sheet with parchment paper.

Gently punch down dough. Divide dough into two equal pieces. Press one portion into each prepared pan, pressing lightly to fit. Use fingertips to crimp edges about halfway up side of pan to make a border (so gooey butter will not run underneath). Use a fork to prick a few holes in dough to prevent bubbling (do not prick dough all the way through). Divide gooey butter into two equal portions; spread over dough in each pan. Let stand, uncovered, 25 minutes.

If you like, instead of using two 9" pans, you can use one 9x13" pan. Using a 9x13" pan will provided a little more dough throughout the cake (a little thicker). If you use a 9x13" pan, you will only need to use about 4/5's of the gooey batter.

Place pans on prepared baking sheet. Bake in preheated 375 degree oven 20 minutes, then reduce heat to 350 degrees and bake 15 minutes. Topping should be bubbly and golden brown. Do not overbake; topping will not be gooey if cakes are baked too long.

Remove pans from oven and transfer to wire racks to cool until the topping settles and cake is just a bit warmer than room temperature. Sprinkle tops with confectioners' sugar. Serve warm or at room temperature.

Yield: 2 - 9x9" cakes; 9 servings each or 1 - 9x13" cake; 12 to 15 servings.