Step 1

Position a rack in the upper third of the oven; preheat to 350 degrees. Use a little butter to grease the inside of an 8-by-11-inch baking dish, then line it with parchment paper so that two sides of it hang over (to use later for lifting out the slab).

Step 2

Combine the butter and both sugars in the bowl of a stand mixer or handheld electric mixer on medium speed for 4 minutes, or until quite fluffy. Add the eggs, one at a time, beating until fully blended before adding the next. Stop to scrape down the bowl.

Step 3

Add the oil, milk and vanilla extract; beat (medium) for 1 minute, then remove the bowl from the mixer.

Step 4

Whisk together the bread flour, all-purpose flour, cocoa powder, sea salt, baking powder and baking soda in a medium bowl, then add to the butter mixture. Stir to form a blended dough, with a few streaks of flour, then add 2 cups of the mini marshmallows, 1 1/4 cups of the chocolate chips, all the puffed rice and 1/2 cup of the slivered almonds, stirring gently until evenly distributed.

Step 5

Pour half the soft dough in the baking dish. Scatter the caramel candy halves over the top, then cover them completely with the remaining dough.

Step 6

Scatter the remaining 1/2 cup of mini marshmallows, the 1/4 cup of chocolate chips and 1/4 cup of slivered almonds. Dampen your hands with water, then use them to gently press those top bits into the dough, and make sure the dough goes into the corners of the baking dish. Bake (upper rack) for 20 minutes; the top marshmallows will be melted. Transfer the baking dish to a wire rack to cool, which may take a few hours.

Step 7

Use the overhanging parchment to lift out the brownie slab; cut into 15 or 30 pieces of equal size.