Makes 4-8 wafflewiches
1. To make the filling: Combine the water, butter, sugar, cinnamon, and salt in a small saucepan. Cook over medium-high heat for about 1 minute, stirring constantly, until the butter is melted. Remove from the heat, add the pecans, and stir for about 1 minute (the mixture will continue cooking from the residual heat). Add the vanilla, stir to combine, and set aside until ready to use. The mixture will thicken a little as it cools.
2. To make the waffles: Combine the milk and vinegar in a large bowl: the mixture will curdle and become like buttermilk. Stir in the oil, sugar, maple extract, and salt. Add the flour, baking powder, and baking soda and stir until smooth, being careful not to overmix.
3. Cook the waffles according to the waffle iron instructions using nonstick cooking spray. You should get 2 Belgian-size waffles or 4 standard-size waffles. (For extra crispness, toast the waffles in a toaster oven before assembling and eating.)
4. To serve, break the waffles into quarters. Add 2 tablespoons to 1⁄4 cup of filling on top of one quarter, then top with another quarter. Serve warm.