Line a 20 cm / 8-inch square baking pan with parchment, leaving an overhang on two sides to use as handles. Chop the dates into pieces about the size of a raisin.
Toast the oats, sesame seeds and sunflower seeds in a dry 26 cm / 10-inch skillet over medium heat for 5 to 6 minutes, stirring often, until golden and nutty-smelling. Tip them into a mixing bowl and stir in the dates, cinnamon and salt.
Warm the tahini and honey in a 1.5-quart / 1.4 L saucepan over low heat for about 2 minutes, stirring, until loose and pourable. Take it off the heat and stir in the vanilla.
Pour the warm tahini mixture over the oats and stir with a spatula for 1 minute, until every oat is coated and the mixture clumps when squeezed in your hand.
Tip the mixture into the lined pan. Press it down hard with the bottom of a flat measuring cup, working into the corners, until the surface is level and tight.
Chill for 60 minutes, until firm. Lift the slab out by the parchment and cut it into a 4 x 4 grid with a sharp knife to make 16 squares.