Preheat and Prep: Preheat your oven to 350°F (175°C). Line an 8x8-inch or 9x9-inch baking pan with parchment paper, leaving a bit of overhang for easy removal.
Cream Base: In a large bowl, cream together the softened butter and dark brown sugar until fluffy. Beat in the egg and molasses until completely smooth.
Whisk Dry: In a separate bowl, whisk together the flour, oats, baking soda, salt, cinnamon, ginger, cloves, and nutmeg.
Combine: Gradually stir the dry ingredients into the wet mixture until a thick dough forms.
Fold in Mix-ins: Dump in the chopped dates, sultanas, cranberries, chopped nuts, and seeds. Fold them thoroughly into the dough until evenly distributed.
Let the Batter Rest for 5 to 10 minutes in the pan, before putting it in the oven. (This gives the oats time to soften and absorb the liquids.)
Bake: Press the thick dough evenly into your prepared pan. Bake for 20 to 24 minutes. (Check them at the 20 minute mark; whole wheat can dry out quickly if overcooked.) The center should feel set but slightly soft to the touch, and a toothpick inserted should come out with just a few moist crumbs. Cool and Slice: Let them cool completely in the pan before lifting them out using the parchment paper. Slice into bars or squares.