In a 4- or 5-quart heavy pot, heat oil over high heat until candy or oil thermometer registers 380 degrees.
With bread knife, cut challah lengthwise. Then cut each length in half, resulting in four equal quarters. Remove crusts from each quarter, in so doing shaping challah into large triangular wedges.
Mix cinnamon and sugar together in a small bowl. In a large bowl, beat eggs thoroughly and then slowly whisk in cinnamon sugar until fully incorporated. Add vanilla, salt, and milk, continuing to whisk.
When oil has reached 380 degrees, place two challah wedges in egg batter. Soak for 30 seconds, then turn over and soak other side for an additional 30 seconds. Remove from batter, shaking off excess. Place wedges in hot oil. With tongs or slotted spoon, turn wedges every 30 seconds or so, until all sides are deep brown, about 3 minutes.
Remove wedges from oil and drain on paper towels. Keep warm in 200-degree oven. Repeat process with remaining two challah wedges. When ready to serve, plate wedges and dust with confectioners' sugar. Serve with maple syrup and, if desired, fresh fruit on the side.